couple of months ago, was also established on the ILS 7R, autopilot engaged, stable and all of the sudden aircraft pitched down very rapidly and violently.....immediately disconnected ap, recycled FDs, and able to salvage approach.
Yes they offered Rnav on the Atis but company not authorized for Rnav, and believe Atis said possible GS oscillations- thought they meant it might scallop a little up and down, really wasn't expecting that.