Hmm, that's odd. Truth be told, I was never one to advocate for kernel swaps, since I basically know little to nothing about it, but I have noticed that kernels have an impact on the performance of most vital parts of the phone (when I messed something up and flashed an A12 kernel on the OOS A11 official build, I managed to fix my slow camera lens switching issue, but wifi stopped working completely, as well as the fingerprint reader - sort of to be expected, but I was surprised that the camera started working better than before!). I know that others didn't have the slow camera issue, but I haven't heard of others facing the issues you're facing, so I really can't be for sure. But yeah, if you ever do get the itch and return to OOS, try flashing different kernels (and backup the original one ofc) and see how things change - I think this won't interfere with GPay functionality, but I could be wrong (we either don't have it here, or my Mastercard just isn't accepted for some reason)