Thanks, for the log, unfortunately it shows no error for Heimdall just the starting sequence. Did you send this after restarting Heimdall?
I do notice 63 reports of devices not ready when Heimdall starts, Heimdall will continue and they will be added letter when (if) they become available so that shouldn’t be a problem.
The strange thing is, when you manually reboot there doesn’t seem to be a problem but after a firmware upgrade there is a problem. Could you please report that to Athom specifically mentioning that.
Also, when this happens, could you please go to https://tools.developer.homey.app/tools/system and check the videoCoreUndervoltageOccured and videoCoreUnderVoltageCurrently values?
Or install the Homey System Internals app [APP][Pro] sysInternals - Shows Homey’s System Internals and check that.