Apple 6 Watch charging take 5 + hrs.

My Apple 6 watch charges normally up to 85%. This takes the typical 70 min to charge from 10% to 85% with no problems. But when hits 85% the charging stalls. It gets stuck at 85% for 90 min. +. To charge from 85% to 100% it takes another 3 hrs. I have authentic plug and charger original to watch.and I removed plastic film. Watch is only 10 months old. I purchased from Best Buy. Any suggestions on how to speed up charging? Thanks.