RB67 advance issues with any film back including unused, new in box ones.

[Certain Exposures]

Every single film back I have used with my RB67 ends up failing to advance film correctly while using it out in the field. I purchased a new, allegedly unused (and I believe it based on the box, plastic, and condition) 645 Pro SD film back and it did the same thing on the first roll (which happened to be this photoshoot).

I have had this camera and back and a lens serviced already. The lens is ok. However, the body and film back returned with familiar operational problems, including this one. The repairman said he could not replicate my issues. Do any of you have any theories about how this is could be a 'me' problem?

When I shoot a roll, eventually, the 67 or 645 back does the following:

1. The lever keeps advancing past the point it should instead of stopping.
2. If I continue to pull the lever it gets locked all the way out.
3. The film frame counter stops in a random position in between frame numbers.
4. The red 'exposed' flag in the film counter appears and doesn't go away with subsequent turns of the lever.

Every single film back does this randomly on most rolls.

I can get around this when it happens by guesstimating the stop position and using the double exposure feature. That is no way to enjoy a photoshoot, though.

 

[mshchem]

I would suspect dryed out solidified grease. I've had issues with old Hasselblad backs not stopping at 1. I have used a bit of a solvent, and freed it up. This is common with beautiful old unused cameras. "Shelf Queen".

 

[MattKing]

It is an issue with the safety interlocks.
The fact that it happens with several backs tells me that it originates in the camera.
Does it happen with more than one lens?

 

[Certain Exposures]

Yes, it happens with several lenses.

 

[MARTIE]

Long shot... does it only happen when attached to a tripod?

It's unlikely the repairman uses it on a tripod.

 

[Certain Exposures]

I only use the camera on a tripod because I find it awkward and heavy to use handheld. Why do you believe the problem would be caused by a tripod?

 

[MARTIE]

I've known the screws can be (overly) tight and mess with the camera.
Easy to test.

 

[itsdoable]

I only use the camera on a tripod because I find it awkward and heavy to use handheld. Why do you believe the problem would be caused by a tripod?

On some cameras, there have been cases where the tripod screw is a little to long, and distorts the bottom of the camera, causing issues like this.

 

[Certain Exposures]

OK, are there any threads out there where someone has realized that this impacts a RB67? I will search in the meantime. I am surprised because it seems so unlikely. I don not see a connection between the tripod mount and the safety locks or advancing.

 

[MattKing]

The other thing that used to affect me regularly was a very minor issue with the rotating adapter. If you don't rotate the back fully to either of its rest positions, the interlocks don't necessarily behave as expected. A slightly worn rotating adapter makes that more likely.
The issue with the tripod mount is probably sort of similar - anything that slightly prevents the parts of the camera from lining up the way it was designed to can confuse the interlocks.
And of course, all of these factors can end up working together.
A lot of RB67 bodies and backs and rotating adapters have seen a LOT of use.