Unfortunately I have encountered both the problems you describe, but cannot shed any technical light on the causes, less to say that they are aerodynamic. The pitch up is a bit disconcerting, especially at night, as it can be as high as 20/25 degrees. I had put it down to the SPAS applying a correction to the stick position as a result of the applied cyclic when correcting the pitch up, but have since come to the conclusion that it is an instability problem. When it happens you get the distinct feeling that you have no pitch control for a couple of seconds.
If your interested you can also get locked into a tight left bank in the BK. Once again I found myself in this position doing a low level exercise and thought I was about to literally slide slip into the ground from about 20 feet with full opposite (right) stick displacement. Thankfully it held its height (only barely) as it decelerated in the uncontrolled turn, from about 80 knots to 5 knots in less than 3 seconds. Scared the crap out of me. I have since found that applying a small amount of opposite pedal and forward cyclic will bring the old girl out of any high angle of bank, albeit with low G’s.
Your right, it’s a pretty well know problem and one I think we just have to deal with from inside the cockpit as it is probably inherent in high performance helicopters.
Give my best to your monkey,
Cheers