I have an albino pacman frog, and he keeps flipping on his back. I heard this could be due to stress, but i dont know why it is happening all of a sudden. Ive had him for a few years and everything is still the same.

10 gallon tank
1 albino pacman frog
humidity 70-80%
80-87 degrees on one side, about 10 degrees lower on the other
decholrinated water
coco husk substrate
live plants, water dish, heat lamp, light, automatic mister
eats crickets
gets vitamins and calcium, a mixture of both at each feeding
light on during the day off at night
heat lamp
eats once or twice a week
pooping fine
just cleaned the tank

what could be wrong?