I have been having the same issue I have changed nothing, always charged just fine in the nice open space I have it in. I took a family vacation so didn't charge it for a few days but when I did get it back on the base it was at 36% . While charging it got warm and faulted out and hasn't charged to full since. I even did a reset on it.
I have exactly the same problem after upgrading to Tizen version 184.108.40.206, if I put my smartwatch on the charger with AOD on it gets very hot and charges to 74 percent but in power saving mode it charges to 82 percent and still gets very hot but if I turn the watch off and put it on the charger it doesn't get higher than 68 percent and gets hotter than before and gives an error message.
This is an issue that a lot of people are having lately, specially after upgrading to latest Tizen version 220.127.116.11 and/or 18.104.22.168. There is a thread on xda about this problem too but nobody has a solution yet.
This is the xda link :
What I don't understand is that with so many people having the same problem with the same product and almost all of them after upgrading to the latest version of the firmware how come Samsung doesn't take this more seriously?
They should've come up with a follow-up firmware where the problem was addressed and solved permanently, if you read the messages from the xda thread and in this thread it'll become clear to you that it's a software issue and it does not have anything to do with faulty hardware in most of the cases.
Thanks and I hope Samsung comes with a solution as soon as possible.
Try to charge your Gear with buttons down. It works for me. With buttons up charge stuck at 85-89%. With buttons down watches charging to 100%.
I am a reseller of all kinds of electronics, in 2018 I had 2 x S3 Classics with the same problem as wall as 1 x Frontier, the problem is not the cradel or the charger niether is it the battery, the problem is with the watch, I have swopped cradles and chargers, I imported 2 x new Batteries, installed one today , still the same I tend to believe the firmware issue, faulty firmware or corupt update