[ninja_zx11]

Yet another problem:
After having disassembled/reassembled the unit a few times, I now have problems getting the head detected correctly.
If I connect it via usb, my pc tells me, that it has detected an unknown device, rather than a VAS5054A. After several tries, it then suddenly detects the unit correctly.

Any hint, what may case this?

I guess a bad solder point, but where to look first?

I found on some clones that AMB2300 module is soldered permanently with the main board and dissembling upper and lower main boards is kind of difficult and puts lot of pressure and with a pressure board flexes too and could be creating problems.I made amb2300 removable by removing the solder joint and now i can safely disassemble it if i need to.

Regarding your problem,Not an expert but can only suggest you to carefully inspect the area around the USB chip on your Vas5054 with a magnifying glass.