[Richard]

I only have one valve, and it is associated with the rear slide manifold. That valve is three full turns open. From the position I found it, it took three full turns exactly to close it.

So bear with me a minute. I can't get the little I know about the intermittent operation of your slide out to line up with the valve being the only problem. The valve was either closed off or it wasn't. It would not adjust itself. To the best of my knowledge, the slideout did work sometimes, and sometimes it did not. Is that true? Also, you said the slide did not move at all when you hit the retract button. Knowing how the HWH system hydraulics work, the system pressure holding the room out would have released, and the room should have twitched a bit, but you say it did not.

My concern is that you may not have found the problem, and it is waiting to bite you again at an inopportune moment.

So, I would use an engineering trick. If the valve was indeed the problem, then close it, and see if the slide fails to operate. Easy enough to confirm the root cause.

If it retracts with the valve in the original position, I would start suspecting a loose connection or a relay in the HWH control system starting to fail.