I just had this issue. My aids are 6 months old. And while my left ear has significantly worse hearing than my right, for the first 6 months, the battery life discrepancy between the 2 sides was small. I had no issues getting through long days with plenty of streaming.
A couple weeks ago, left aid started fully draining in about 8-9 hours, right aid would be at 50-60%. Furthermore, it would start changing volume and programs at random, as well as disconnecting from my phone and not being found. Then it simply died after a week and wouldn’t charge or turn on. I got in to see the audiologist, and the original plan was just to swap out the battery to see if it solved the issue. When he opened the aid up, the inside was rusted to quite the surprise of us both. I have never submerged these aids in water, unintentionally or otherwise, or even really gotten them wet at all even with the IP68 rating. The right aid did not have any issue.
I was give a loaner/demo pair the office had while mine are sent in for repairs, and I noticed that my hearing in my left was clearer than I had with my original aids. When I first got my aids, I had commented to my audiologist that sometimes it sounded like the mics on my left weren’t always clear, and after a restart, it would seem to be ok. Now I suspect I had a defective left aid to begin with, and when I got my aids, there was already traces of rust inside and it progressively got worse. When I get my aids back, I am hoping it will be a complete replacement of the left. If not, I may request for it given my observation after sending them in.
So, in your shoes, I’d ask my audiologist to pop open the aid as if he/she was going to replace the battery and examine the inside quickly. I would like to think my case is an outlier, but given you’re having some problems I just had, can’t hurt to check. Good luck.