model condition using parent object's formula field not working in partner community unless lookup field is required on the page layout

This is a very strange problem that had an even stranger solution, but just in case anyone else comes across this, hopefully you don't have to spend 10 hours on it like I did.

Scenario: model on MyObject__c custom object has a condition "MyObject2__c.FormulaCheckbox__c != true". Works fine in standard salesforce, but in a Partner Community I was getting the error "java.sql.SQLException: ORA-00936: missing expression" 
Could be related to this known issue: https://success.salesforce.com/issues_view?id=a1p300000008XwYAAU&title=a-soql-from-a-community-p...

The error went away when I made the MyObject2__c field on the MyObject__c page layout a required field and then refreshed the fields on the MyObject__c model in the skuid page.