list projects API request returns "500 Internal Server Error"

Summary

A GET call to the latest API appears to fail when trying to list projects

Steps to reproduce

We are running version the 8.11.4 b871b762 version of gitlab locally. The API was functioning well previously and some requests work, e.g.:

GET http://mygitlab.com/api/v3/groups?private_token=xxx

returns a valid JSON containing the groups.

However, the equivalent call for projects:

GET http://mygitlab.com/api/v3/projects?private_token=xxx

yields:

 {"message":"500 Internal Server Error"}

I have currently attempted restarting gitlab with no avail:

sudo gitlab-ctl stop
sudo gitlab-ctl start

I have also tried using another users private_token and also get a 500 error.

I may be doing something wrong, in which case, any help appreciated.