Mamiya 7 film advance slips or skips

I have an intermittent problem with my Mamiya 7. Sometimes film advance goes fine. Sometimes, however, the lever advances but you can tell the gears are not engaged and the film does not advance; you can just keep moving the lever back and forth forever w/out it locking into the next frame. I've found that if it is engaged and I advance it and then release it to flop back as quickly as possible, it continues to engage and advance most of the time and I can get through a roll that way. Not good though.

I've seen somewhat related problems in searches but nothing that diagnoses this particular problem. So:

Anyone aware of the mechanics of this problem and the fix?

If not, anyone aware of a shop that currently works on these cameras?

Any advice appreciated.

Jeff

It sounds like your clutch is slipping. Seriously. Time to take it in.

Thanks Jim any suggestions on where I should "take it in"?

MAC used to be the preferred vendor but mamiya is handling repairs directly now.

I think I have seen mention on here of Precision Camera Works. No personal experience though.

Send it to Precision Camera works in Illinois. I wouldn't trust anyone else. Note-- there are other PCWs in the United States. Pay them no mind, and only go through PCW in Illinois.

Dead Link Removed

They recently bought up all of MAC's Mamiya 6 parts, and they of course service Mamiya 7s as well. My 7 was serviced by them in 2012 and was handled well.

Thanks for the responses!

Hello

I just bought a Mamiya 7II from the first owner. He bought it new in 2013 and did maximum 60 rolls. It is first time I have M7 in hands but I think there is something wrong with film advance lever.

While loading it with 120 film I noticed that the film advance lever slips considerably. It seems that when I rotate the lever slowly there is less slippage but am not yet sure about it. The slippage might depend on how fast I rotate the lever or maybe there is just a certain 'point' inside the mechanisms at which it slips (irrespective of how fast I turn it).

I am attaching a link to a video showing how it behaves. Could you please take a look at the video and opinion if it's normal. Because the lever slips I have to turn it back to its initial position. You can hear at 0:07, and also later, that there is no clicking sound - the lever is slipping.

Thanks

Forgot to mention: so far I've done just 2 rolls. On the first I got 9.5 frames, on the second full 10 frames. The frame spacing on the second roll, except for the first 2 frames, was even, and equal to about 6 mm.