The flex grid doesn't play well with layers. Removed ALL layers, started with an extremely small part of a project.
I need to have only 3 cells (sorry, I'm old and the flex grid reminds me somewhat of Lotus 1-2-3 from the 1990s) that I need to display. I need them to align evenly top to bottom. What I see in the WWB screen should be very close to what I get in a modern browser.
I've added margins so that all portions are identical in size. The bits of text are inside of shapes (rectangles) so that there is no chance of a variance in size between cells, or so I thought. The three main images have margins to make their dimensions exactly the same. (this is the 768 breakpoint ... but at least it still attempts to center itself (I tried turning off centering in the page, things inside of the cells get left aligned), unlike the 480 and 320 breakpoints.
So, here's what I see in WWB.

and here is what I get in Firefox

and here is what I get in Edge

This link is to a zip file with both the wbs file and the images:
http://www.ahgweb.com/wwb_14/more_flexgrid_problems.zip (about 7 megs)
The problem is on the page called "attempt_1".