Don't know if this is any helpful or just displacement activity out of dispair and helplessness but I found an old Windows XP notebook under my table and did the firmware flash from there. But with no success (apart from remembering why I had switched to mac years ago, hell what a plague this was...).
Eventually I got the firmware flashed to Ansible and again on the actual version cycles voltage becomes stepped with the first power cycle (actually the second power cycle if you count the one that is necessary to leave bootloader mode).
Again no problems with the intermediate firmware from early december that is not amongst the github versions.
Is it really that I am the only experiencing this? With two Ansibles? In two different cases?