Mamiya C33 jamming :(

[Carter64]

It's been a while but yesterday took the Mamiya C33 out. Everything seemed to be fine until I got to the 5th frame. Then it wouldn't wind on. The crank was solid, as though it had already been wound on.
Lenses off, lenses on (two lenses), lock/unlock lens etc, grasping at straws. Eventually I got it to move by cocking the lens manually, slowly and partially pushing down the shutter release while gently turning the crank, and this took two stages.
After that, it was fine and I finished the roll.
I was wondering if anyone else has had this?
Would a CLA possibly find and/or cure the cause? It'd be a shame to junk it as cosmetically it's exec+ and once past this jam, functioned perfectly.
When I unloaded it, the film was wound on perfectly to the spool, so I could rule that thought out. Oh and it dry-winds/fires no problem, too.
Losing two frames every time I take it out will be irritating, to say the least

 

[freecom2]

First thoughts - lubricants seizing up, or debris in the winding mechanism. However, that is purely speculative, and in truth the only way to find out is having the camera looked over by a competent technician.

 

[Carter64]

Thanks, I really should do that. Probably should have done it before now, I have no idea of the history of the camera. I've owned it a couple of years but it's rarely been used.
I also found something on-line, that the lever needs to be pushed completely down to release the interlock, and not to be hasty and let go when you hear the shutter fire.
Another case of 'panic first, research later'
Either way, a good CLA as suggested will at least give me some peace of mind.