Unexpected page changes with button click

[bestcampus]

I am currently using Delphi 10.1 Berlin with IntraWeb 14.2.3...

I am trying to "update" an ancient application (written in IntraWeb 4) and have hit a problem. 

When the page with tabs initially renders, it looks perfect.  If a button is pressed (or something that actually causes the page to post), then the "tab section" of the page becomes "garbled".  Looking at the HTML/CSS source BEFORE and AFTER the button click shows portions of the CSS missing (such as width information).

Is there something I can do (besides upgrade, which is not an option) to resolve this?

Thanx,
Chuck