Pixel 7a battery issue

I have a batterry problem for around a week now. Battery seems better. Its draining a little slower than normaly. But between 30 and 70% (each time its different) in a few seconds it goes to 20 and 3 and 0 and shutdown... I found only 1 post about this and there are no good answers and its on Reddit: https://r.darrennathanael.com/r/pixel_phones/comments/1f3qdh8/pixel_7a_battery_issue/#

Im running GrapheneOS so warranty is probably voided.