Battery draining while charging

I'm on watchOS 4 since it came out and now my series 1 Watch is not charging.

I put it on the charger and the green lightning bolt indicator is showing but the battery percentage keeps dropping. I'm down to 3% already. I switched to an iPad charger and that didn’t help. Now I turned on flight mode, and it quickly went up to 7%.

Any ideas how to fix this?