I've experienced it a few times in the 212.
I flew a 212 equipped with SCAS and hydraulic linear actuators (instead of electromecahnical), it was originally a CAA machine.
It use to get into pylon rock if you were slinging with the SCAS on. It was never a problem with the SCAS off. IT felt (in the hover) like someone was pumping the cyclic fore and aft and side to side.
It probably had poor transmission mounts.There was a check you could do in the hover to check the transmission mounts but I can't remember as its been years.