It fails in a particularly poor way because the <section …/> tags are placed immediately after |- on the same line, in the same place where the HTML attributes for the table row would go. This results in <tr … typeof="mw:ExpandedAttrs"> in the Parsoid output, which we don't recognize as a real table row in VE. I'm not sure if Parsoid handles this entirely correctly.

We should support that better (in the worst case, we could mark the table as uneditable in VE).

My advice on how to make this work better today:

• A) Move the <section …/> tags to separate rows: https://test.wikipedia.org/w/index.php?title=Table_with_section_tag&diff=prev&oldid=564196&diffmode=source. This should work the same when transcluding the section, and should work better in the editor since VE will recognize them as separate metadata nodes between table rows, instead of a weird markup on top of the table row. It's not a commonly-used part of VE though, so you might discover some new bugs… [edit: It seems like they're not treated as metadata, and sometimes lost when editing. That's another bug.]
• B) Move the <section …/> tags inside the table cells: https://test.wikipedia.org/w/index.php?title=Table_with_section_tag&diff=prev&oldid=564198&diffmode=source. This is the way that is the easiest to handle for the editor, since the tags are treated as just normal table cell content. It would require some changes to how you transclude these sections, though.

Many thanks for the advice! ☺️