KTM not alone
The first time I experienced a clutch that didn,t release was on my 01 Beta,The problem was still there on my 05 Beta. The longer they sat the worse the problem. It got so when Idroppedit in gear after it sitting for a week I would be certain there wasn't anything in front of me. Very common problem with Beta. I spoke with the importer and he said to use Motul in the gearbox.which doesn't help for 4 strokes. He also suggested cleaning the fiber plates and roughing up the steel plates to help stop the stiction. The greatest benefit was noticed by the switch in oil. My suggestion would be clean the plates with brake cleaner. and go with a recomended MOTORCYCLE oil.