You could try to upgrade to a newer version.
From the app store under modeler you can see all releases and view the release notes to see if your particular issue has been resolved in a newer release.
For the Mendix 4.x line, version 4.8.11 contains all patches released in the Mendix 4.x release.
In order to get recent (security) patches we advise you to upgrade to a higher major version.
See for more support info: https://docs.mendix.com/howtogeneral/support/
Product Support Period: Mendix supports the current major release and the two prior major releases (and we support each major release for a minimum of 24 months). Because of this, we recommend that you upgrade your projects to the latest version of the Mendix Modeler at least once a year.