Airpods pro 2nd gen - volume level random increasing or decreasing

I have noticed this problem while i was in bus to work, it seems like sound out of nothing its silent i increased it and after a moment its too loud and i dont know why.

I was looking at hearing and out of nothing it went down from 73db to 67db and i havent seen th bar on left showing volume lvl has changed, the song was noticibly quieter and i must manually adjust it at my optimal lvl.

I have no indea what could cause this, i have turned on sound normalization on spotify, latest firmware on airpods, latest ios update.

I am using iphone se2020 and on airpods is only noise cancelation turned on

Thanks for effort to help me

and sorry for my bad english