It appears that the reverse proxy cache was sending the wrong version of some of the web resources. Once this cache was refreshed, functionality was restored.
Diagnosing the problem
Resolving the problem
Using the fiddler option "Disable Caching" allowed the test workstation to function properly and also appeared to update the proxy cache, as all other workstations started working as well (even without fiddler). Likely, we could also have requested that the proxy devices get reset