"For me these days, though, it's more during the movements during the technique that I find myself in a "weak" position. I might be nitpicking on my own incompetence too much, but I feel it's there... "
We practice (slow) techniques to prevent this sometimes where uke "acts the maggot" and tries to pull tore off balance (he shouldn't suceed), but really the only sure thing you can do is show your problem to a good teacher and ask him to show you where you're going wrong. Even a simple body movement can be too complicated to describe adequately in writing....
And when you do try a slow technique for this, remember..... YOU'RE STILL DOING IT MUCH TOO FAST!
Oh, and T'ai Chi might help too.