Enlarged Listbox doesn't capture mouseclick

I finally decided to add breakpoints on the start of various events.
The two weird things that happened on clicking in the Listbox were
Half of the time the first TextArea, which had focus would fire gotfocus even though I clicked on the ListBox.
The other is I am using MouseUp to get the row, instead of CellClick. When it did the RowFromXY and Column it returned a -1. I think it got the correct location (400 and something)

How could it get -1?

Edit a few minutes later
Hmm I ran into a similar problem a couple of years ago and I think I might try my solution from then - move stuff to CellClick.

Here’s the link.
what-causes-rowfromxy-to-fail