Specifically, running under emacs -Q commit d6dc66053d846b6fc041889b4d0f383c8dac4da3 of 2021-05-30 on GNOME, if I load up https://github.com/raxod502/bug48170-repro, then `next-line' navigates 1 line down, but `previous-line' navigates 2 lines up!

Any ideas about what might be causing that?

Best,

Radon