So I have a form with a Pass/Fail field that is automatically set with an equation.  This of for electrical testing, so I have some fields with the Ω and Ø symbols.  Forms let's you use those symbols and automatically puts them in the variable name.  Using those variables in the formula works fine, with no errors, and the preview shows the formula works as expected.  Then, if you test using a form that is already in flow (in a task/step and not the starting/initial form) it also works fine, most of the time.  Sometimes it would throw an error after submitting saying the formula was invalid, I wasn't able to determine why sometimes it worked and sometimes it didn't.  What is also interesting is that on the starting/initial submission of the form it failed consistently (throwing invalid calculation error) until I changed the variable name to not have those special characters.  It's to bad Forms doesn't make this limitation more obvious in some way.  (I am on v10.2.1.246)