Sally, I'm assuming Robart units or a copy? Regardless, the same is true for all designs.

if you require inverted to get them to unlock you likely have an issue with the uplock end binding on one or both. I would suspect the mass lever from the long legs and wheels are creating too much load on that end of the slider and preventing it from moving the all-important first few thou.

Unfortunately those long legs also magnify any binding or loading at the wheel end of the legs. You can have the same problem with the trunnions binding in the housings when retracted, most often the result of mount surfaces not perfectly true. The fact you have to flip it inverted to break them loose pretty much confirms you need to release that weight to have the gear cycle, so doubt physical binding is the cause. In fact, a few makes add a spring to help counter the gear weight to aid in pulling them up into the wings, but that works only when the gear is cycling.

One trick would require removal and that can be really annoying with the linkages and such. Once out, splitting the halves will show how the slider locks the trunnion each end. You may have to sand or round off a slight amount to allow them to break loose easier.

Only work on the retract end as it sounds like you do not have any problems getting them to retract.

I worked on enough, but only used mechanical retracts once myself and with the Harvard/Texan they did not survive long. More the fault of the aircraft geometry than anything else and I am currently on the 4th or 5th iteration with servoless, custom trunnions and modded Robart legs. In fact, last Saturday was the second good landing I ever had with it.

Personally, I figured mechanical setups far too much work to rig, required very stiff linkages that would hopefully not flex under load and the likelihood of even a slight misadjustment would have the servo continue to try and complete the action, (sucking on the power system continuously as it did so) was the reason I never used them again. Servoless will shut down in a few seconds of a bind condition.

Regardless of version, best have a healthy or even separate power system for retracts.

Well, we're off to the rally soon. Wife is a bit iffy on room so the Bear may stay home