I have the exact same issue - although I can flesh out more details. I originally thought the issue was with the buds, but it’s not.
If I listen with just the left bud, sound seems right. Just the right, or both left and right and the right bud is much lower than the left. (For good measure, I have cleaned the buds in multiple ways, no effect). I noticed that if I start audio mid-song, the initial 0.1s in the right bud will be “normal” in terms of sound level then it goes back down to lower level (the left doesn’t change level). And it’s with any audio on my Phone(1) (spotify, pocket cast, etc.) so it’s not app related.
I thought it was either the OS, or the buds at that point until I noticed that it did the same behavior while connecting to my car audio system (no buds). So it’s an OS issue. Multiple Googling shows that Oneplus and Pixel users also have that problem to some degree. It seems to be related to BT. Tried all options I could in settings and developer options, nothing fixed it. According to the internet, it seems to be related to BT power optimizing, but whether that’s true or not, I can’t say, as I’ve yet to fixed it.
