Hello Stephen,
I would need more information about your setup especially what version of mendix studio are you using? Are you using the Mendix Edge plugin? https://marketplace.mendix.com/link/component/218436
Mendix in version 9 does not support reverse proxy beyond the root URL Domain which is unfortunately not the case for Industrial Edge. For single page mendix apps without login it works somehow but not stable. The reason it works is because the URL in browser is not changing.
To make it work, first to to use the Port forwarding in docker-compose. That should work smoothly.
We are currently testing if the new version of mendix 10 is supporting the reverse proxy.
See here as well. https://forum.mendix.com/link/space/deployment/ideas/2892