If it works in safe mode then it should be a theme/theme component that’s interfering (you can narrow it down to just theme/theme components using the safe mode tickbox options if you want to confirm).
If you have a look in the inspector where you’ve been toggling off the display none you should see a clue as to where it’s coming from:
That should give you the theme id of where the rule lives. You can then add it to a link to track it down - eg [YourSite]/admin/customize/themes/83