Air carrier pilot reported glideslope indication deflected full scale on approach. Flight crew disconnected autopilot and continued approach using PAPI guidance.

Narrative

I was pilot monitoring. We were cleared and conducting an ILS approach to Runway XXL. Weather was VMC. Approach was stable and normal. The Flying pilot had the autopilot engaged for the approach. It was briefed that the PAPI s were available for a visible aid for the approach path. I was about to make the 500 stable call when the glideslope indication went full scale down. The aircraft initiated a downward pitch to follow the glideslope. The flying pilot immediately disconnected the autopilot and flew the PAPIs to maintain the stabilized approach. I verbally also said bad glideslope; fly the PAPIs . I then confirmed we were still within stabilized approach criteria and said 500 feet stable. Pilot flying responded landing. I then told ATC we lost the glideslope. ATC replied it might have been because of an aircraft holding short of XXL on taxiway (north side) . The aircraft holding short was a B 767. The landing was normal. During taxi to the ramp; we asked ATC for a number to call to speak about the glideslope failure.On the way to the hotel I called ATC on provided number. I briefly spoke with a ATC employee who then transferred me to an ATC supervisor. We had a cordial conversation about what happened. We discussed when ATC is required to protect the critical area and agreed this wasn't a required situation. I explained that even in VMC conditions when we are cleared by ATC Approach for the ILS approach; we fly that approach as such until we transition to a visual aid (ie PAPI). I also explained that we can leave the autopilot coupled to about minimums (company specified limits) if we so choose. I explained that we don't anticipate losing the glideslope signal unexpectedly. Our conversation centered around sharing information with each other so that hopefully we can continue to work together towards a goal of safety. The Supervisor said he would look over the data they record and see if any issues could be found. I thanked him for his time and we concluded the conversation.