C6903 charging process constantly interrupts

[Shitblast]

Hello. Over the last three months, especially magnetic charging has become gradually more problematic. When charging, the charging process will charge for about ten or fiteen seconds or so, then interrupt for a second or so, and then continue for another ten or fifteen seconds, and so on it goes. This would only happen after deep discharges at first, but then with the battery more full, all the way up almost full. I then switched to USB-port-charging, and this worked well at first. Then the same problem started repating there as well. The problem is the same with different chargers and in different houses. I did a factory restore, and that seemed to help a little, but not much. What might this be?

Edit: And the battery lasts a little over two days with normal use.