Text in table cells -- can't figure out why it gets bigger when I click it

I can’t figure out which CSS selector is influencing this behavior:

I have a table using the built-in table maker.

When I click a cell, the text is slightly larger than it was before, say 12pt from 10pt. When I click off, the cell goes back to the smaller size.

This behavior is messing up my clicking in table cells, obviously. A sandbox vault works as expected/desired.

I tried disabling Style Settings, which didn’t help.

I tried disabling Minimal Theme Settings plugin, which didn’t help.

I tried disabling Minimal theme, which helps.

In the Developer Tools, when I click to edit a table cell, the text’s DIV simply changes from

<div class=“table-cell-wrapper” style=“”>

to <div class=“table-cell-wrapper” style=“display: none;”>

Thanks for any suggestions what to try next.