Battery slowly charging on Tab S
I have approx 300 Samsung tablets in my company (including ~100 SM-T805). I understand that this could be a software issue with your ROM etc, but in our experience, we often do find that the cables can slowly degrade over time, and even though they display that they are charging at full speed, the speed is actually well below the original maximum.

I would suggest you find an alternative cable to test. Drain the tablet battery to 0%, power the unit down and test a full charge with the current cable, (e.g. 2hr 12mins) and then replace the cable, and re-charge the tablet from 0% again.