It is super freaky, right?!?!
I recently got some new speakers that I leave the grills off. I mostly stream and when I played some records a couple weeks ago I jumped up and raised the tonearm. My old speakers have the grills on and they are very difficult to remove so I suspect this has been happening for a while. It does not seem to cause any harm to the speakers but it sure is difficult to watch. I did some research and got all the same stuff people are posting here. My issue is not isolation, I solve that a while ago, I suspect mine is the mismatch between the cartridge and tonearm. I haven't tried to resolve, just one more deterrent for records...ugh. That's another thread as my digital sounds just as good on most albums and I am losing the desire to mess with records. Best of luck in figuring it out. Let us know what happens.