Node not connecting, blinking D20 led

I am using the MDEK10001 developer’s kit and I have one unit that the D20 led always on (no other leds blink). It is not discoverd by the Android app and it is not made part of the network.
I cannot reproduce it, but it happens one in a while and the only way to reset it is to re-flash the firmware. Reset button don’t change anything. I connected it to pc from the port usb and set different modes (nma,nmia,nmt,nmtl,nmb) it hasn’t changed anything. Removing the battery sets it to D20 fast blinking.

I will be running some senarios on location and under time limit and I cannot unscrew the unit to reflash the firmware when this happens.

Does anybody know anything on how to debug this issue or at least help discover why this happens?

(there is also a '18 post MDEK Kit is not working)