Comparing two commits often incorrectly reports "nothing to compare"

Summary

When using the Repository -> Compare functionality for comparing two commits, very often GitLab reports "nothing to compare" even if the commits have differences. Doesn't seem to be a problem with branches and tags.

Steps to reproduce

Open Repository -> Compare. Enter a commit number in the From field, and another in the To field (with both from the same branch!). Click compare. For us, this usually leads to the message "There isn't anything to compare. You'll need to use different branch names to get a valid comparison.". Sometimes reversing the order (From/To) solves the problem, very often it doesn't help.

Expected behavior

A normal comparison

Actual behavior

Usually leads to the message "There isn't anything to compare. You'll need to use different branch names to get a valid comparison.". Sometimes reversing the order (From/To) solves the problem, very often it doesn't help.