Wasn't there last weekend but I've done two overnights at Waverly over the years and the fourth floor corridor is genuinely strange. Not in a "spooky feelings" way, more like the environmental conditions up there - the air movement, the acoustics, the light bleed from outside - create a perfect recipe for pareidolia and peripheral vision anomalies. That said I've seen footage from multiple unconnected groups that shows something similar in roughly the same location, which is harder to dismiss.
What floor was this on and roughly what time? And was anyone using IR lighting or just standard torches? The reason I ask is IR can throw up some odd artefacts depending on the kit, but it can also reveal things standard light misses. Curious what other people who were on that particular weekend are saying.