All 3 dump valves stuck open 2008 2955RL

[HOOK]

I have a suggestion. There is a housing with the shaft running through it that goes to the valve itself . Likely the problem is that rust has formed between the two. Remove the rear angled plastic wall from the service closet. Remove the handles and retainer nuts from shafts. Hold the flexible shafts so you can put rust penetrant down the housing , a little at a time , until no more will go in. Allow to sit for a while. Try them , if they move, work them until they free up.