"After using it a bit more regularly, I found that this problem went away. "
That sounds right. I have the Widelux, very similar set-up/mechanism. The actor, Jeff Bridges, has a great website for his Widelux which explains this and some remedies. If it's too far gone, it has to be repaired but he moves the mechanism and exercises it a bit which keeps it limber...yeah, I know that's not technical and I'm anthropomorphizing it a bit.
Theres a link to how I load it on my review of the S3 pro (essentially the same camera) here
Sounds like its banding.
its an endless pain, this horizont/horizon 202/ s3-pro-drama which started 30 years ago for me. 1981 in moscov the responsible export firm technointorg and fototass didnt want to help. it seems the producers did not learn enough from the past. find a good repairman to fix your 202 forever. we even replaced the drum. slit-opener must be stabilyzed by adding locktite. lens of s3-pro must be replaced by 202-lens since its new lens isnt not sharp anymore more at fstop 16. wrong design.