Apple Watch keeps disconnecting from charger

My Apple Watch (Series 5, two years old) keeps disconnecting from its charger. It seems to be fine until about 50% charge, and then it disconnects and reconnects every 2-3 minutes which is extremely irritating because it pings all the time. I have already searched the forums and tried a number of suggested things to see if it will fix the issue:

1) restarted the watch

2) checked to make sure the software is up-to-date

3) checked my charger, its connection, changed powerpoints and power sockets

4) tried other chargers (all official Apple chargers, including the one that came with the watch in the first place)

Other than this issue, the watch works perfectly fine. Is there some other fix?