I wonder if the warning is because you are trying to using the same collection 12 times. I was not aware of a soft limit on that, but it is possible. Someone with @webflow could chime in.
You could test this by adding another collection list from a completely separate collection. If the error does not then occur it would point to the same collection limit I said was possible.
Looking at your preview link, I find 20 collection lists inside of the all months agenda symbol. It seems that you’re using collection lists for the days of the week labels. If those labels don’t have to be dynamic, then I suggest making them static text and removing those collection lists. That would bring you back below the 20 limit.