• the battery clip itself is fine

    The holder did come off the board in two cases after putting the battery in.
    So basically the pressure (on the solder points) was so high, that it came off.
    I learned from that and resolderd the other 2 Pucks before putting in the battery.
    So it definitly IS a problem with the holder or the "new" kind of batteries (used VARTA CR2032 2pc Lithium Blister / EAN: 4008496746460).

    The video is misleading in the way, that there is a contact problem, but he mentions, that his batteries are thicker too.
    I do NOT have a caliper to measure the batteries and inside e.g. an Apple Airtag they seem to be perfect (also due to the different holding mechanism).

    Since the name is "2032" one can think that it is 20 mm x 3.2 mm but as always some people like to break the rules ;)