MArketing Promotional Pop-up takes the whole screen when configured for lower left locaiton

Site URL: https://chriszforma.com

sometimes my promotional pop-up that is configured to show up in the lower left corner displays very big and covers the whole page.

I can't find the cause.  it doesn't happen all the time.  It has happened in Chrome and in Edge on Windows and Chrome on MacOS.

Attached is proof of the lower left configuration for the popup (and what is expected for location)  and attached is a pic showing it taking over the whole screen. 

When it is happening and I "refresh" the page it continues.  There are scrollbars shown but nothing visible moves when scrolling as the popup is covering the whole page, though the scroll bars reflect the amount of content below the popup.  

also, it is configured on "Display and Timing " to show on "Any first page" "Show on timer and Scroll", "Immediately", "25% down" and enabled for "Show on mobile" 

anyone have any idea what causes this?