My Vitessa T was my 1st 35mm camera (handed down to me from my dad, c. 1972) and it made sharp, contrasty slides for projection. I cannot solve your particular question, but I can tell you that it was a malfunction with the film advance mechanism (the "combi-plunger") that caused me to trade in my Vitessa around 1980. It appears that the combi-plunger was the Achilles heel of these cameras, which were otherwise so pleasurable to use (built-in meter reading in Exposure Values which were "remembered" even when you changed shutter speed or aperture; the magical sliding depth-of-field indicators; and the synchro-compur shutter which was quieter even than the Leica M3 and which had flash-synchronization up to 1/500 sec.!) Given all this, if you've found a work-around to the advance mechanism that works for you, I'd say Leave Well Enough Alone (unless someone else comes up with a definitive solution).
Please post some of your shots! Which lenses do you have?
"It's so heavy! And it's full of numbers!" --- teenaged niece upon meeting my M3.