ya, sometimes I fix one thing then another failes...... I just gotta keep my shoulder up, opps, now pulling it, opps now I am dropping my shoulder..... etc.
just remember, when you go for prctice, throw a game of all 10 pins, only looking at your target, then a game of 7 pins, target only. now if you keep leaving pins from your mechanically perfect throw, and you will because a perfect ball will leave pins sometimes, at least you can spare it.