If possible, please send the .framework file of your document type association (from the user who is experiencing the problem), so we can investigate. Send it to email@example.com
or use the https://www.oxygenxml.com/techSupport.html
page to submit the file.
For the Windows user that reproduces the problem, please also ask them to use menu > Help > Report problem
and Submit a report. I'm particularly interested in the Plugins and Frameworks they have. Details from the report may also show other potential causes.
Do note that XML catalogs from any frameworks (document types) may interfere, if your users have other custom frameworks.
I'm not sure if XML catalogs are the cause of this problem or not, but they are a potential cause. I can implement an XML catalog that purposely causes exactly what's happening to your Windows user, so I feel this needs to be investigated before we can rule it out.
After a validation, please save the catalog messages from the user with the problem to a file (right click in Catalogs tab and "Save Results as XML"), zip the XML file (if large) and send them to us (email or support page).