Help Needed Fixing Cassete Player

I have this portable (garbage sonashi SWM-38) player that can't hold speed. I have tried just opening it up and ajusting speed but by the time i put it back together it is already too slow. Also like 90% of the time it is slower.

I have checked the belts and they are in seemingly enough tension.

There is one way i have found that it works and it is very weird. When i press the play button just enough so that it plays but not enough for it to latch and i can let go it plays at pretty much perfect speed.

I am certain that it is the player as all the cassetes play at a constant speed in my non-portable player