Tone arm bounces

This very weird! When I play an album at a very high volume my tone arm starts to bounce. It will play albums start to finish at moderate levels with no problem at all. I have checked alignment and weight issues and they seem to be good. Clearaudio Avantgard table with Stradivari cart. The system is in a temporary room and may not be ideal. Could it be bass from my rear ported Watt Puppy 6's? Thoughts-----------

Bill