After leaving it in the cupboard for a while, I just shot 2 rolls of B&W 120 film on my Holga and had them processed and scanned by a local lab.
I expected that I wouldn't get perfect images out of my Holga, but on both sets of negatives I am seeing weird light leak like artifact across pretty well all of the frames in both rolls of films (which I have never remembered seeing before). And these artifacts appear a lot sharper than I would attribute to a leak in the camera itself. So I am trying to narrow it down to either a leak in the camera, my film handling or the labs film handling and processing.
Here is an excerpt across the top of a single frame from both of the different films. The first excerpt is the last frame in the roll, and the second excerpt is from the middle of the roll.
The artifacts are mostly noticeable at the top of the frames, but I have noticed some frames that having matching artifacts vertically aligned on both the top an bottom of the same frame
As requested, here are pics of the contact sheet that was produced from the negs that shows the full top of the frame. I've highlighted the areas of interest. I'm beginning to wonder if the answer to my question is ¿Por qué no los dos? Because on one frame the "leak" doesn't extend past the frame and is very symettrical (which was in the middle of the roll), but in the other a very sharp line extends up to the top of the neg, and is not symmetrical (and was the last frame in the roll)