Android DFU library not working for Samsung phones on Android 10

[Mxoh]

We use both the iOS and Android DFU library to support DFU through our mobile application. Recently we found that Samsung phones running on Android 10 have a problem with DFU both on our app and when using the NFR Toolbox. Strangely it shows DFU disconnected on our app but Gatt error in the NFR Toolbox.

We never had a problem with DFU on iOS before. And after various rounds of testing with different with Android devices we finally narrowed it down to Samsung + Android 10 to cause this DFU failure. On other Android devices that run Android 10 for example Huawei and Xiaomi does not encounter any DFU problems. And Samsung phones on other Android versions do not encounter this DFU problem too. We even had a Samsung phone that was originally running Android 9 and it worked for DFU but after upgrading this same device to Android 10, DFU stopped working. 

I wonder if this is a known issue as more and more Samsung devices on Android 10? And any suggestions on how to troubleshoot and fix? 

[Scott--R]

We have just discovered the exact same issue in the last 24 hours. I hope there is a fix for this. We have also discovered that secure DFU works for us using an Samsung phone running Android 10 but a legacy DFU does not. We've tested various phones and have also narrowed it down to specifically Samsung phones running Android 10, and specifically legacy DFU.

Hopefully Bjorn or another Nordic Guru can help. This issue is 100% repeatable in our testing.