Permissions Error on Member that doesn't exist
In SSMS if you open each role and find the Measures Dimension Data security section then go to the Advanced tab (if you have trouble finding it see this blog for screenshots from the same screens in SSDT-BI) do you see any role mentioning that problem measure? If that measure doesn't exist in the cube then remove it from the security role definition. 

If that doesn't help you find it then right click on the database on SSMS and script the database as an Alter then search the XMLA for that measure and post back the section of XMLA where you find it.