500 error the first time spam detection kicks in, when submitting an issue
I've seen this twice today on GitLab.com - most recently around 18:10 UTC
Editing an issue to add more links seems to cause a 500 error the first time I submit. Pressing "back" then re-submitting immediately gets me the reCAPTCHA page instead. Solving and submitting allows the issue to be edited.
The 500 error should be in sentry. It could just be synchronicity, but worth checking.