Thanks for the heads up. I left those parts out on purpose because I knew that if I made a mistake in the room and item definitions, that was the quickest way to get it. Thought I put that in my OP, but it seems I omitted that. Sorry.
So I spent some time with three windows open to try figuring out the problem. I found it.
It ends up that I am using the extension "'Liquid Handling' by Al Golden". That one requires a second Golden extension, "Supplemental Actions". Supplemental actions separates "sit" and "enter" as synonyms. In fact, according to the accompanying documentation:
SIT, STAND, AND LIE are now separate commmands from ENTER.
Which begs the question, do I have to now create two clauses under the "Before" rule, or is there a quick and easier way to re-synonym-ify (like that coinage?) those words?
Honestly, I can see the utility of having those words no longer be synonyms, but I think that the utility is rare enough that it shouldn't be part of an extension that will see so much work.
OK, rant over.