Slow display of job trace

When I load https://gitlab.com/gitlab-org/gitlab/-/jobs/614028470, it seems to take 5-6 seconds just to load the job trace. As far as I can tell, the backend responds within a second for the needed endpoints, so why is this slow?

If I download the job.log and record a performance trace in Firefox, I can replicate the issue. Attached is the Firefox profile.json: