ACI_EVT_HW_ERROR line 571 nrf8001

Question

I am using a nrf8001 and the arduino aci library ported to work with my project.
I have started from hello world example.
Connecting to the device from android app, sending some data over the uart and then disconnecting seems to be mostly working fine.
After some time I get something like this in my debug output 
 C5 :5, F, 0, 0, 50, 0, 
 Advertising started. Tap Connect on the nRF UART app 
 E3 :3, 84, F, 0, 
 E4 :4, 81, 3, 1, 2, 
 Evt Device Started: Standby 
 E25 :19, 83, 3B, 2, 6C, 6C, 5F, 6C, 6D, 2E, 73, 30, 2E, 63, 0, 18, 23, DB, F9, F0, 36, 28, A0, D9, 0, 0, 
 HW error: 571 
 6C 6C 5F 6C 6D 2E 73 30 2E 63 0 98 23 DB F9 F0 36 8 A0 D9 0 0 0 
 C5 :5, F, 0, 0, 50, 0, 
 Advertising started. Tap Connect on the nRF UART app 
 after this, the device does not seem to be advertising anymore and requires a power cycle to get it back to working. 
 The markings on the chip are "NRF D 8001 143900" 
 Any help would be greatly appreciated.
Thanks 
 seems pretty similar to this question
 devzone.nordicsemi.com/.../

Elliot · Accepted Answer

I think I have figured out why my chip was stopping.
Occasionally the RDYN line takes longer than I had expected to become low after REQN was pulled low.
I had overlooked the fact that the library pulls the REQN line low forever while it polls for the RDYN line to be low.
I had other things for the micro to be doing and one of these things used the SPI. So on these occasions when RDYN took too long I was doing SPI with REQN left low (RDYN could come low while the other tasks had priority) which unsurprisingly seems to have been the cause of the nrf8001 stopping working. 
 Now my question is:
If I pull REQN low but then I need to do something else before the RDYN comes low is there any problem with me putting the REQN high while I do other things and then pull it low when I have time to deal with the nrf8001 again?
I am trying this now and it seems to be working fine.