Bad phonak receiver

I replaced my Phonak M90s with L90s. In my left HA (my good ear, very little gain needed) streaming music or shows had a very distorted bass (rattling like a blown-out speaker), even at low volume and with the low frequency gain tuned way down. I swapped the receiver (M) from my old M90 into the new L90, and that fixed the problem. I’ll be returning the defective receiver. My audi was really surprised that the problem was the receiver. Has anyone else experienced this?