Same batteries, different remaining charge in two XR 11s

Commands to my Contour 2 XR 11 remote were slow to the point of being almost unresponsive. Yeah. I know. All batteries eventually die, right? I was ultimately able to navigate to Remote settings where the on screen charge remaining read 5% (no wonder it was so lethargic). I thought this peculiar, as I distinctly recall doing a similar battery level check a couple of days ago when it read 50%. I then changed the batteries for that XR 11.

I then took those two batteries that allegedly were down to 5% and put them into a different XR 11 in another room. According to Remote settings on that Contour 2 screen, there was 50% charge remaining.

This is truly a head scratcher. Who else has had similar experience? Better yet, who's got a plausible reason for it?