Menu going behind grid headers

Morning,

I upgraded my from 2.70.8 to 2.80.3 this morning and upgraded the css using the application settings & save steps. The application has this css in the style.css file to overcome the issue where drop down menus in a page header were going beneath grid headers in the body:

.rz-grid-table thead th {
  z-index: 1 !important;
}

This worked as expected in 2.70.8 but, following the upgrade, the css style is still in style.css file but, menus are again going behind the grid headers. I've inspected in Chrome's dev tools and it is showing this:

image

Am I missing any steps that might need doing on upgrading?

Thanks!

We are not aware of such issue (menu going behind grid headers). There were such issues in the past but they should have been fixed out of the box. Can you provide more information how to reproduce this problem? Does the problem appear with an unmodified theme?
menu-grid-headers

Here is a test application for reference.
DataGridAndMenu.zip (9.3 KB)

Thanks for the test application. I played around with the layout file unsuccessfully so, I created the layout again from scratch and this time everything is working as expected. I'm not sure what happened to the original layout file but, something obviously was changed which broke it - it was quite an old layout that has been tweaked lots of times.

Thanks for your help!