Gear Retraction Issue

[Scudrunner]

Good day, new to the forum. Ive owned my 1974 337G for 3 years now. During our first annual our AME (A&P) discovered some incorrect wiring on our landing gear. He fixed it and I should note we have the gear door removal stc.

Long story short typically when I do my walk around I pump the gear extension handle down with the master off to check for critters making a home etc then when I go flying the gear retracts normally without issue.

When I don’t pump the gear handle prior to a flight which is usually when I fly somewhere then depart a number of hours later or the next day.

When selecting the gear up, the gear will not retract. I select the gear switch back down and pump the handle a few times feel the pressure build and stow it and select gear up and it retracts normally.

My Mechanic has worked on a few 337 over the year but they’re not common. He is definitely the type that knows his way around the aircraft and I and everyone trust his work.

I need to get this solved and I’m planning to bring it into the shop and attempt to figure this out. But before I drag it in as the weather changes has anyone encountered this issue or could provide some guidance.

Thanks