Grouping tag not synchronized with iTunes

Audirvana Mac 3.5.29 (3559), iTunes 12.9.5.5
When I add a grouping tag in iTunes it´s not synchronized to Audirvana. The same is true in the other direction: adding a grouping tag in Audirvana is not synchronized in iTunes. Both apps add the grouping tag to the file: I controled that with yate.
Are there any propositions for solving the problem? Thank you!

Hello @o99, when you are experiencing this issue, does iTunes and Audirvana are open at the same time?

Hello Damien
When both are open, but after closing both and restarting Audirvana after the sync the grouping is not synced.