It seems like you have several different concerns tangling with one another, which makes it hard to tell what's causing what. Leaving aside any possible equipment failures, it seems like there are three completely separate problems:
- You haven't gotten the hang of focusing with the Bronica's screen;
- You're shooting at some very slow shutter speeds and getting camera shake;
- The Bronica's meter is too responsive for the way you use AE.
I think you can address the third by simply not using AE; it's kind of a crutch anyway and makes it very hard to learn about exposure. A few rolls shot on sunny-16 principles will teach you more than a few hundred shot with AE!
As to the second, I don't think anyone can handhold a camera that size at 1/4 with any consistency! 1/125 or 1/250 will serve you better. That may mean opening up or using faster film, but the large negative means the tradeoff between speed and grain is less important than in 35mm.