Absolutely correct, Gentlemen, NOT brake fluid!! My bad typo - really bad!! Transmission fluid is what they recommend for an "emergency top up". A specific grade of Dexron or eqivalent - check HWH website.
Having downloaded their maintenance manuals I confirm do not use silicone lubricant. They recommend only WD40 for cleaning and lube if required. Also state do not wipe off dirt without soaking with WD40 first - dry wiping can cause scratching and leaks. They also state to wipe off excess WD40. So they use it for both lube and cleaning and specifically state to use WD40 to clean off any silicone if it has been used.
As to my jack problem - turns out if was low fluid level in the tank - very low!! The filler cap was not tight, but no leaks anywhere, so I assume it was not checked and topped up properly when it was originally sold. Very difficult to get at in this particular model MH. Narrow compartment and tank is behind the pump/valve assembly. Have to do it by feel and/or mirror. I made a special long thin filler funnel. Put a quart of HWH fluid in (Camping World). Ran the purge both HWH and the dealer told me to. (Jacks up hold down manual retract buttons for a few seconds.) Different from the generic maintenance manual. Apparently the 725 system has an auto purge method. Works perfectly now but still needs at least another quart for correct fill level.
But beware - another service company told me it could not possibly be low fluid, hmmmm.... not as expert as they claimed or angling for installing a new jack?
If not for Mondays, Tuesdays would suck.