my sharepoint 2013 nintex workflows are all failing to start on one site, but all my other sites work fine. it doesn't matter what I put in the workflow (ie: update field, copy item, etc...) and it doesn't matter if I have the workflow set to "manual" "create" or "modify" - same error, every time.
here is the full error message:
"Failed to start workflow. Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression."
this doesn't happen on any of my other sites, and I've checked all the settings under "manage site features" and "site collection features" and they have the same activated elements on both sites...?