Subject selection lost when importing the catalog

Hi,

I'm having issues with the automatic subject selection masks, maybe someone can help me understand.

I only recently updated Lightroom and started using the AI masks.

When working with photos on a white background I'm using the subject selection reversed on the background in order to brighten it and make it perfectly white. 
I work from home on a catalog, when I work from the studio I have a backup of all the catalogs I'm working on, so when I get there I usually open the backup catalogs and import the ones I've worked on at home.

I discovered that, after importing a catalog where I used subject selection masks, all the changes I've made are still there but said masks are gone...

When I import a catalog I use the "only metadata and develop changes" option, always worked fine.

Am I doing something wrong?

thanks!