Hi Martin;
Can you try the following ...
1) Perform a FULL BUILD on your PB 11.5 based PB App & correct any Errors or Warnings.
2) From the PB 2017 IDE - run the Migration Assistant against your PB 11.5 PB App's source code. Please correct any errors or warnings the MA discovers in your PB 11.5 source before attempting any migration.
3) If Steps#1 & #2 are OK - please optimize all your PB 11.5's PBL's! Then do a Full Build again.
4) Make a copy of your PB 11.5 App's source into a work folder just for PB 2017.
5) Now migrate the PB 11.5 from the PB 0217's work folder.
Suggestion: A bad DB client driver can take out the PB IDE with extreme prejudice (aka GPF). Try connecting to another DBMS like SA. The PB IDE only uses the DBMS connection at DW Object migration time - but in fact, does not depend on the current DBMS for that. If that helps your migration to PB 2017 - then switch back to SS when you are fully migrated.
HTH
Regards ... Chris