Lightroom Classic does not show Image-caption after import of Raw-files

Dear Community, 
my workflow is (since many years) to first view my images (Sony ARW-Raw files) and add Caption and Copyright info in the programme Photomechanic https://home.camerabits.com/tour-photo-mechanic/ .

My problem is, that after importing the raw-files (and the xmp-files) to Lightroom Classic the image caption (from photomechanic) is not seeing or showed any more by Lightroom Classic. The Caption-fields in Lightroom Classics are empty, the information gets lost (in Lightroom and after exporting from Lightroom).

I think I didn`t change any import preferences in Lightroom Classic (V. 13.5.1 / Mac OSX Ventura 13.5.2).

Does anyone ever had the problem or has an idea on how to solve the issue in Lightroom Classic?
I contacted Photomechanic support and everything with the written metadata is fine. 

Many thanks, 

Heiko