That’s very interesting!
Now I wish I hadn’t reset my battery today so I could try and replicate your experience.
Mine’s always charged to 100% from what I’ve noticed
It’s not temperature related that I am aware of. The issue exists at warm or cold temps from what I’ve seen.
Maybe resetting your BMS fixed mine. 
Mine would always show 100% after being docked, until the snow came. Then mine would only go to 96% and hang out there. Until yesterday, when it went back to 100%
I bet the bug does have something to do with temperature