Fluctuating ILS glidepath signals are not uncommon. Usually always caused by large lumps of metal (ie aircraft on the ground) moving between you and the transmitter. I’ve seen it at VHHH, KLAX & YSSY. In all cases it has been in VMC and ATC therefore are not required to protect the ILS signals. Pilots are expected to use airmanship and commonsense. Call me old fashioned, but when it has happened to me I (shock, horror) disconnected the autopilot, looked out the window and hand flew a visual approach.