Occasional '403 Forbidden' with passenger on apache

Question

I have an issue with a rails application running under apache with passenger. The issue is that occasionally I get a '403 Forbidden' response. This starts happening on seemingly random occasions, and randomly goes back to normal.

Looking at the logs when this happens, there is nothing coming from the rails application or from passenger. In the apache error log, I see lines similar to the following:

[Mon Jun 24 19:45:14.395393 2019] [core:trace3] [pid 9660:tid 140391642806016] request.c(312): [client 132.72.41.24:44668] request authorized without authentication by access_checker_ex hook: /he/teaching/spring2019/courses/fourier-analysis
[Mon Jun 24 19:45:14.398040 2019] [core:trace4] [pid 9660:tid 140391642806016] util_script.c(571): [client 132.72.41.24:44668] Headers from script 'spring2019':
[Mon Jun 24 19:45:14.398074 2019] [core:trace4] [pid 9660:tid 140391642806016] util_script.c(572): [client 132.72.41.24:44668]   Status: 403 Forbidden
[Mon Jun 24 19:45:14.398086 2019] [core:trace1] [pid 9660:tid 140391642806016] util_script.c(653): [client 132.72.41.24:44668] Status line from script 'spring2019': 403 Forbidden

So it seems that for some reason Apache considers part of the url to be a script rather than passing it to passenger. I have no idea what is happening, or how to debug it further.