Every time I try to upload a new firmware over version 1.2.2 or 1.3.0, using "flash -u COMx AudioMothx.x.x.bin", the Flash utility fails at the first attempt with message "ERROR: Timed out waiting for send confirmation from AudioMoth". The device is then left in an apparently "bricked" condition, with no LED activity when connected to the PC via USB. However if the Flash procedure is repeated, after disconnecting the power, the device connects correctly as a USB serial device and the Flash utility behaves correctly and re-installs the firmware (any version).
This behaviour is repeated every time I attempt to flash the firmware - ie Flash fails at the first attempt but succeeds at the second. The problem only occurs if the existing firmware is AudioMoth1.2.2 or later - when up/down-grading from AudioMoth1.2.1 or earlier Flash will always succeed at the first attempt.