Hello,
new Skiper version with updated Attributes export for JoinColumn, InverseJoinColumn, JoinTable, Index, UniqueIndex is available for download.
Please test it and let me know if it solves all issues you had.
https://www.skipper18.com/support/402/downloads-skipper-beta
We had to implement several if-def sections and refact some import/export but based on our unit testing everything is working smoothly.