A family of Microsoft relational database management systems designed for ease of use.
Check your PK definitions on those tables. If they are using nvarchar, change them to varchar. That change got rid of the issue for me.
@Lisa Greenwood, OMG thank you so much :-D Have a DB I wrote nearly 20 years ago (started with Access 2.0 :-O ) that is still business critical and one simple lookup table suddenly went #Deleted :-( quick change to varchar and it's back up and running :-D