This is a 3820 stick, (which was the replacement this past June for the 3800 I returned to Roku), the 3800 went through a phase of eating batteries itself, then was OK. I was fed up with replacing them, so I went to rechargeable, which were lasting 2 weeks to a month then longer, so something had changed).
The unit auto updates, & had been at 12.5.0 for a while (but I've seen 3 different builds) still had the original batteries since June (so OK the batteries bit the dust, removing them though they still tested relatively good), So possibly this started with the last "build" of 12.5.0.
I've gone through 3 sets recently (past few weeks) now (all test OK upon removal) & looks like I'm going to replace this evening again as it was giving me the warning the past 2 days). I tried the rechargeables again last week they only lasted for one evening, these run at a slightly lower voltage I believe.
I'm going into a different brand of battery tonight to see if these behave any different.