Thetford toilet leaks after new valve

Since replacing the valve the toilet foot pedal was becoming slower and slower to return to the closed position. I contacted the manufacturer there advice was to use 100% silicone grease on the valve parts and toilet. I removed the valve used grease and replaced no leaks.

Update still drips when flushed will contact manufacturer for help and replace value depending on outcome maybe I damaged it?

I've changed the valve twice on my toilet now in 2 years for the same problem (same toilet as the OP's), as well as the flapper seal this summer. I have never changed a valve on any other toilet in any of the RV's I have ever owned.

I have read this model toilet is a bit of a problem child; next time the entire unit will be getting replaced.

Just checked the foot pedal, the notches that operate the valves have a little damage removed the damage with my pocket knife seams to be working now.

Maybe you got a defective valve - call Thetford or the seller - my guess is that they would send you new valve. Stuff happens.

Its the water valve for sure not the vacuum breaker leaking the vacuum breaker was replaced about three months ago. Just checked it the water valve is dripping only when flushed.

look and see if it is the vacume breaker leaking on the toilet and not the valve

Yes

do you have a water regulator on?