1st The backlight in the MX keys works at 50% of times at top. And no, it's not because of the charge level.

2nd when MX Master3 (or MX anywhere2) return from being inactive, it set the buttons into default settings for a short period. This is quite annoying cause I use volume up and down in the place of previous and next functions. So very often when I try to put volume up or down the mouse completely messes the media. Please try to make some kind of software update to fix this problem.