Mp40es making intermittent out of alignment noise

[Radioheadx14]

Bought a used mp40 with the ecotech driver w/ a mfr date in 9/2011. It's very quiet, most of the time. Ever 15-30 minutes it sounds like it gets knocked out of alignment for 15-60 seconds then the noise stops. I've noticed it the past few days. Normally, you can only hear the normal motor noise.

Is there something that can be done to address this?

[rainmkr07]

try realigning the dry side a little bit. mine does that from time to time, and once i adjust the back a little it usually goes away.

[Radioheadx14]

Seems the more I try to adjust it, the harder it is the align it. It's doesn't rumble when turned up high, but when I have it around 50%, which is how I run it, it rumbles every now and then.

[Breakbeats2334]

I had this same issue double check your glass thickness i never realize this after having these pumps for a long time but your width glass thickness is different then your length glass thickness so double check that. Along with turning the pumps to 100% and aligning them to make them quiet (one at a time is best) so you have the best judgement on noise. I had a fellow reefer sit on a the couch and tell me when its the quietest since its not a big deal if its loud when ur face is up against the tank but it would be very annoying if its loud when your sitting down. Im 4 ft away from my tank and i can barly hear my pumps except when all of them are at 90%-100%