"You can't do that in a ..Handler procedure" with arrayselectedbuild

I have a text display superobject in which I’m trying to display a list of items that are selected in another database. When the formula of the object is


It works fine (gives me a ¶-separated array of all items in the database), but with


I get the error “You can’t do that in a …Handler procedure.”

Any insight into what is happening here?

Oh, never mind. It fixed itself apparently.