CI buffer output size wrong (or its displayed size is wrong)

Summary

When the output log of a pipeline run is somewhat long, I see a truncated output log with a line similar to

Showing last 50257 KiB of log

at the top. The exact number may vary, but it's always close to 50000 kiB.

However, what is actually shown is close to 50 kiB. 50 kiB of output log is really short and often not useful.

Steps to reproduce

I don't know how long the log has to be to trigger this behavior. But I get this with all "long" logs.

What is the current bug behavior?

gitlab.com shows "Showing last 50257 KiB of log", but the output is not anywhere near that size -- it is the last approximately 50 kiB of truncated output.

What is the expected correct behavior?

gitlab.com should show "Showing last 50257 KiB of log" at the top, followed by the last 50257 kiB of truncated output.

Relevant logs and/or screenshots

Output of checks

This bug happens on GitLab.com.

Results of GitLab environment info

Results of GitLab application Check

Possible fixes