Hi folks. I'm trying to complete L1 Model Building online and I've hit an error in adding formulas to the REV05 Price Growth Rate Staging module. When I try to add the formulas as directed here:

I get the following error:

I've double checked that all of the modules referenced in the formula have been set up according to the training instructions. I've also tried building the formulas manually in Anaplan as opposed to copy/pasting them from the training. Same error either way. Any help?