@abomma : You can try checking:
- if the folder in which these files are uploaded is covered under a DITA profile that includes the custom schema catalog
- if the DITA profile that covers this folder does not report any error on the UI (generally represented with a warning symbol, and has details of error under it)
- if the order of catalogs in the custom DITA profile lists the custom catalog on top
If none of above works, you may raise a support ticket to check the scenario on your setup.
Question: have you recently setup this environment or DITA profile or catalog?