I have the displeasure of being a regular ME in a local theater which has a bunch of these still in use. I despise every hang and focus. Thanks for bringing back the nightmares, I just got over em.
Except that they consume 750 watts and put out a pitifully dim and orange tinted blotch of light that is only a quarter as bright as the S4 that uses 575 watts.
Oh, and don't forget your gloves, because they do get fucking HOT! And don't even try to recycle them because they contain asbestos and lead. And they will burn though gels and gobo's faster than you can blink. etc, etc.....
These were fine lights in their day, and I'd chalk up any troubles you are having to abuse and lack of maintenance rather than fixture faults. Ten year old, beat up Source 4 units aren't any fun to work with either.