Can you show a screenshot?
Can you reproduce in Troubleshooting Mode (Help → "Restart in Troubleshooting Mode…”)?

When I go to "Report Errors...", I get

[unrelated errors removed — D.S.]

appName => Zotero, version => 7.0.11 (x64), os => Windows 10.0 17763, locale => en-US, extensions => Better BibTex for Zotero (7.0.5, extension), Zoplicate (3.0.7, extension), Zutilo Utility for Zotero (4.0.1, extension), DOI Manager (1.5.0, extension), Better Notes for Zotero (2.2.7, extension), Actions and Tags for Zotero (2.1.0, extension), ODF Scan for Zotero (2.0.48, extension, disabled), ZotFile (5.1.2, extension, disabled), Notero (1.0.0, extension, disabled), MarkDB-Connect (0.1.5, extension, disabled), ZotMoov (1.2.15, extension, disabled)

Actually, I did. The screenshot shows that it is in the troubleshooting mode.
It is there.

The tooltips on the main panel (not in search) showing for partially displayed fields are fine. I wonder how exactly the red popup is rendered.

@PChemist: The errors are probably unrelated.

ZoteroObjectUploadError: Note 'Contents78152_fmFront Matter...' too long for item '7464892/V4DMG8HK'"]

Probably the same as here:
https://forums.zotero.org/discussion/comment/469114/#Comment_469114

Thanks, this will be fixed in the next beta/release. (The style code that adds the red background goes all the way back to Zotero 1.0, somehow, but it doesn't seem like we've ever gotten a report about this before.)

Fixed in 7.0.14