Can you attach a sub with the "bad" line?
thx for the file... I get white background color. What is your single line max length ?
It's 42, and I've tested this with a clean settings file:

seems like it's considering Line < 42 instead of Line <=42.
I've deleted my settings.xml + decreased single line max length to 42 + opened your sub - then in both main view + fix common errors step 2, the list view line 92 shows white background color...
Hm, just saw it...
Yep. Working great.
You can close this with the commit if you'd like. <3
Most helpful comment
How is this: https://github.com/SubtitleEdit/subtitleedit/releases/download/3.5.7/SubtitleEditBeta.zip ?