Whirlpool condensor dryer - drum sticking?

I have a whirlpool AWZ 7913 dryer.

A few weeks ago the error lights started flashing all at once, I used the reset combination and it started up as normal.

Ever since the drum stops turning after about 10-30 mins of drying clothes, the motor hums but the drum doesnt turn. I have to turn the dryer off and wait half hour and try again and it starts again. It isnt cutting out right away it does dry for a good half hour sometimes more before the drum stops.

I've taken the back off and the belt is in tact, I didnt try anything else as I really dont know what im doing.

When the drum stops, it turns by hand but seems very reluctant to do so, it takes quite a bit of strength to turn it.

The motor just hums and it blows hot air out, just no turning

A few days ago I left it drying and when I went back out the kitchen the error lights were all flashing again, I didnt need to reset it this time, just turned it off and back on and it was fine.

Any idea what this could be..

thanks