Bug: Autoflow import from word fails when master page primary text frame is 2 column

I have come across some very odd behavior when placing a word document using autoflow.

I initially set up an Indesign document with a single column text frame on the master pages. When I place the 80+ page Word document into Indesign it flows in without any issue and all the required pages are automatically created.

But... if I change the text frames on the Master pages to 2 column rather than one, and adjust the default column gutter width, then the import from Word fails at the Table of Contents every time. There are a few pages of text before the ToC so it's creating maybe 6 pages rather than 80+. This happens when I either change my previously working 1 column file to 2 column on the master pages, or whether I create a new file with 2 columns.

If I delete the ToC from the Word file, it flows into the 2 column Indesign file without issue. And as stated, the Word version with ToC included flows into a 1 column Indesign file without issue. But ToC + 2 columns = fail

Not only does the import fail at the ToC, but there's very odd behavior with the text that does import; Only around the top third of columns are being used before text flows into the next column; deleting a character from a word deletes the whole word; typing in some text works for a line or two then all the text I just typed in disappears...

Given this odd behavior I believe this must be a bug.