Never been to Lemp myself but I'm curious about the cold spot thing because it comes up so often in accounts from that building. Was it a sudden drop or more of a gradual thing as you moved through the space? That distinction matters more than people realise - a sudden localised cold patch with no obvious draught source is a very different phenomenon to ambient temperature variation.
The staircase area specifically has a lot of reported activity tied to it and I wonder if anyone has actually logged temperatures there properly over time rather than just anecdotal "it felt cold." Has anyone done a proper multi-hour session with data loggers placed at intervals up the stairs? Would love to see actual numbers rather than impressions, not because I doubt peoples experiences but because the pattern of when and where it occurs could tell us something.
What else did you notice at the same time - any audio anomalies, equipment issues, that sort of thing?