
I would speculate that it is some issue with the cloth shutter curtain, has it ever been replaced or repaired? It could be a bit worn by now.
I got something similar to those wavy lines when my dog jumped on my changing bag, also the line running along the sprocket holes.Is the neg creased at all? That curve might possible have happened on loading but the RHS of the same frame looks like it could be a light leak
If it was a processing issue I would have thought that there would be no "perfect" image displayed as in second shot.
The ripples and curves, seem to me, indicative of curtain bunching up somehow.
What shutter speeds were used in the problem frames ?