Thanks for your reply.
The details. I've bought 125 Trackers (02-2020) all FW 03.21.04 ref 255, they have all the same configuration settings.
I've, due to Corana, only 60 pieces operational. Used last weekend in a race. They worked all well during the race, but when I want to switch the power off, 20 (!) out of 60 could not switch off (*).
This was the first time I'll used them in real action, before that I only prepared, tested and charched the trackers. This all went well. I'll could switch them on and off, no problem.
(*) Those 20 run out completely empty. A few could not charge again, no lights or signal, they appear dead!!!