I unfortunately had one of the problem F7's. I was in the shop three or four times so I finally gave in and sold it. I also had a 1st version Horizont, the all metal one, and have never had a problem with it. My widelux banded terribly but the Horizont never has. It's quite sharp, has a great VF with inernal bubble level and works well except the spacing between frames is a little on the wide side which is no problem. I have a friend that has the same model and she's never had a problem either. The old version like we have would be a very economical and reliable alternative to the Widelux.
I think I still have the filter rings and will have to look for them. I tool the old filters out and cut gelatin wratten filters to fit. I installed a 29 and an 87c or high speed IR. If I remember correctly the filters come apart very easily and it's very easy to install gelatins. What are the filter frames worth without a case?