Tracking down errors

So someone on my team has a process model with the following error:

There was an error in an expression in Process Model Properties at Process Start Form : Variable(s) not found: local!planType local!addActivity

I can guess that some expression/interface hidden in that start form is missing some local variables (the start form itself has no errors), but the problem is there are tons of expressions in that interface and many of those expressions have multiple levels of nested expressions in them. Short of clicking through these countless expressions until I find an error, is there some way to quickly find which one might be the offending expression? 

Or if I'm reading the error message incorrectly some advice on where I should look would also be appreciated.