iPhone Volume changing despite being dialed all the way up?

I have a IPhone 12 Mini running 16.4.1. I usually listen to music through headphones but on the rare occasion I listen to music straight from the phone I have an issue where the volume lowers itself to almost inaudible despite having been turned all the way up. When I press the volume up button it always shows that the volume is dialed all the way up but nothing changes. Playing the music through the phone speakers also kills my battery completely; Depleting a 70% or higher battery to 20% or lower in less than 30 minutes. It’s not the worst cause I don’t usually use my phone speakers but sometimes I like to play music in the back at work but its annoying to have a constantly changing volume and a dead cellphone by the time I leave for the day. Any ideas?