I flew my '77 Turbo Arrow III a few weeks ago and the nose gear came up but the mains stayed down. I cycled the gear a few times and eventually the breaker tripped. After pushing the breaker in the gear came up. The plane was due for its 500 hr AD on the gear so I had that done and inspected at the same time. My mechanic wasn't able to replicate it after numerous tries of cycling the gear. I just flew it the other day after this and the same thing happened again, mains stayed down while the nose came up. The breaker tripped eventually and I pressed it in and the gears came up. Has anyone experienced this, or have any suggestions to the cause, or potential fixes to this? Any help would be appreciated. Thanks!