it is deffinitly your belt on that scrambler
Mine only does it when I give it full throttle in alot alot alot of water
and it sucks when it does cause it barely moves
my old trailboss 330 did the same thing
If you get a new clutch kit from HPI or just seal it really good you shouldnt have any problems after that

when my belt gets wet I get outta the water quick and rev it in nuetrul and it drys the belt of

 

ty for the information

 

welcome