[Putershark]

That is very strange and I would check for water in the inner hull and install / open and check inner hull drains on any boat that is that sensitive to such a little weight movement astern

This for it would lead me to believe that the hull is already bow heavy from carrying some extra water weight, and the slight weight shift is just allowing it to drain aft and get even more weight off the bow. Pop the mega hatch open and walk around inside it on the deck (not the false floor) and see if you hear some squish of water under your feet as you move about if so, she is water heavy and it needs to be drained off