Hi there,
First off, thanks for the amazing package!
It seems I have found a bug in the 10.3.0 version. When I go to the backoffice on a published website I get the following error in the console:
GET https://testwebsiteurl.nl/sb/umbraco-backoffice-extensions-js.js.v638242280505760400 net::ERR_ABORTED 500
When I inspect the error further I get the following:
FileNotFoundException: No such file exists /App_Plugins/TranslationConnector.Xliff/configController.js?v=10.3.0 (mapped from /App_Plugins/TranslationConnector.Xliff/configController.js?v=10.3.0)
It would seem that in the ManifestFilter of Xliff the javascript files are added together with the version query, which gives issues once they get bundled.
Downgrading from 10.3.0 to 10.2.0 solves this issue, as the javascript files there are added to the manifest without the versioning.
I hope this helps! 
This is a companion discussion topic for the original entry at https://our.umbraco.com/forum/112194-error-in-translation-manager-1030