nrfConnect for Desktop (Bluetooth Low Energy App) ALWAYS results in blank/white application window after some time of use

[rodims]

nRFConnect for Desktop v3.3.0 
App: Bluetooth Low Energy v2.3.2 
Windows 10 x64 ( 19.04,  19.09), using Dual Monitor. 
Device: PCA10059 or PCA10056

I can start, connect, and use the nRFConnect / Bluetooth Low Energy App without problems for some time. For a certain time it works fine and simply as expected. 
The device attached to my PC usually is a nRF52840 Dongle ( PCA10059 ), but I also verified the problem with a nRF52840 DK  (PCA10056)

But after some time the window becomes completely blank/white. 

I have seen some complaints about a white window in the forum, but none of them seems to have the problem that it first works and then turns white after some time. 
The typical scenario is: 

- Start nrfConnect for Desktop
- Start the Bluetooth Low Energy App from the list of apps
- Select the BTLE device (usually PCA10059) 
- Select "Start Scan" to discover my BTLE devices
- Connect to some BTLE device and communicate with it. 
From now on it is only a question of time (seconds to several minutes) when the client area of the Bluetoot Low Energy app window turns completely white.
May be important to mention: when the window turns white, I usually do nothing in this window.  So the problem appears without any obvious reason. 

I can close the window through the Windows captions close box, but clicking into the white window at different locations does nothing. So it's not just a simple Windows Refresh problem, minimizing and restoring the window does not help. 
What is possible is to press Ctrl-R, then the windows content will appear again, but all connections are lost. So thats not more helpful than restarting the Bluetooth Low Energy App. 

So I cannot work with this longer than 5 minutes in average until I have to restart everything. 
This problem is around since I use the nrfConnect for Windows (1 year approx) , so it was also present with previous versions and never worked for me. 

I investigated the log file, which looks ok, but the final problem is not logged there in any way. 

Is this a known problem ?
How can I get rid of this annoying problem in nrfConnect for Desktop ?

# nRFConnect System Report - 2019-12-06T20-02-51.791Z

- System:     System manufacturer System Product Name
- BIOS:       American Megatrends Inc. ALASKA - 1072009
- CPU:        1 x Intel® Core™ i7-6700 3.40 GHz 8 cores (4 physical)
- Memory:     20.6 GB free of 31.9 GB total
- Filesystem: C: (NTFS) 475.9 GB 62.8% used

- OS:         Microsoft Windows 10 Pro (10.0.18363) win32 ia32

- Versions
    - kernel: 10.0.18363
    - git: 2.12.0.windows.1
    - node: 12.0.0
    - python: 
    - python3: 

[Simonr]

Hi

I will forward this to the nRFConnect team, as I haven't seen a similar issue before myself. While we're waiting for a reply, can you think of anything in particular that you do every time when using the BLE app that can help to recreate this, as I haven't seen the white screen yet? I opened the Bluetooth Low Energy app 20 minutes ago and have not seen this issue as of yet. Are you able to test this on another computer to check if it might be specific to the computer you're using?

Best regards,

Simon

[rodims]

Hi, 

up to now I have no method to reliably reproduce the problem by a certain procedure. As said, the actual event seems to occur randomly, without any interaction by me within the app. However it occurs so frequently that I usually will have the problem after 20 minutes. 

I have seen this on another Windows 10 computer already, though I did not verify how often it occurs on this one. 
I would assume that "somehow" there must be something special with my computer/ configuration, because otherwise I would expect many many complaints about this issue. 

Today I tested the following: 

- it is sufficient to select a device / adapter which is connected via USB to the PC.  No need to "Discover Devices" or start a Scan, or do anything else. 

- As already described I tested alternatively with a PCA10056 (DK) and a PCA10059 (Dongle), both show the problem. 

- My PC does not have a speaker, but by chance I once heard a typical windows beep in my headphones, exactly when the problem occured.  So this might be either a standard beep issued by the nrfConnect BTLE app, or theoretically it could be related to USB events ? However the physical USB connection is solid, nothing detached or shaky. 

Looking at the number of permutations (2 different PCs, 2 ( 3) different devices attached via USB, which all produce this problem, it seems as if this is a one time problem. 

[Simonr]

Hi

I let the nRF52840DK run for a while after I replied to you yesterday, and did not see the issue you describe in almost an hour of having the BLE app open and connected here on my side. I'll try again today to see if I'm able to recreate it while we're waiting for a reply from the devs.

Thank you for providing all the details you can think of!

Best regards,

Simon

[rodims]

I also did some short tests with my home PC (Windows 10 x64), same PCA10056 board which I used before). Just starting and connecting also does not show a problem over e.g. one hour.  But I think we should not assume this problem would appear for everyone or under all conditions.  It certainly needs some special condition which must apply. 

An interesting test was the following.  If I send my Windows (not a Laptop) into Sleep mode or Hibernate mode, then after awaking from that the problem appears ! The Window is blank, and only with Ctrl-R or restart of the BTLE app I can fix that (of course the USB connection to my then is also lost). 

I tried to reproduce this on my Office PC (for which I reported the problem), but this does not cause the problem.
Sleep and Hibernate (and the detailed CPU sleep states) may behave different on different PCs, so I would not  expect that they all behave the same. 
However this might help to isolate the problem, if someone can reproduce it. 
It strengthens a bit my suspect that the problem itself could have to to with USB, and the Nordic app to react improper to some unknown USB event in the system. In this case the problem would be part of the Firmware which is automatically programmed into the PCA10056 or PCA10059 upon first use with nrfConnect. 
To repeat: on my Office PC there usually is no obvious human interaction when the problem appears. It just happens out of nothing, i.e. I assume it is caused by some Windows event. 

[Simonr]

Hi again

I just wanted to update you on my testing today. I left the nRFConnect BLE app open during the day while going about regularly with my day, checking in once in a while that it was still up and running, and have now had it up and running without a single error for ~6 hours and 20 minutes. You can see the log below as I tried scanning a few times during the day to confirm it the app still ran as expected.

07:42:26.483	Getting information from J-Link debugger...
07:42:27.951	Found device type: unknown. J-Link firmware: J-Link OB-SAM3U128-V2-NordicSemi compiled Jan 7 2019 14:07:15.
07:42:27.951	Connectivity firmware version: 4.1.1. SoftDevice API version: 3. Baud rate: 1000000.
07:42:27.952	Opening adapter connected to COM13
07:42:28.871	Successfully opened COM13. Baud rate: 1000000. Flow control: none. Parity: none.
07:42:28.872	Reset performed on adapter COM13
07:42:29.993	Adapter connected to COM13 opened
09:10:00.840	Scan started
09:10:05.358	Scan stopped
10:20:39.435	Scan started
10:20:41.285	Scan stopped
13:15:55.199	Scan started
13:15:56.503	Scan stopped
14:02:47.206	Scan started
14:02:48.244	Scan stopped

I will try again with connecting to a device and doing some other stuff tomorrow and report back. But seeing as you say it happens when you do nothing in the app, it seems more and more like the issue is specific to your computer.

Best regards,

Simon