Ok, another update, from sometime around the end of the fifth full charging process.
With the fifth charging cycle, the device started to act exactly as it used to, back when I first bought it. I assume in every firmware update, full charges and discharges up to five - six times is necessary for the battery drivers to work correctly.
For now, I'm staying with 1.5, and I hope this will be the last post I'm sending to this thread
Kind regards
Seref