[Bug?] Highlight for Active Split Sceen Missing Post New Update

As it says above.

Prior to the update, when I toggled to a split screen, whichever editor I was working in, the header was highlighted in blue. That is no longer happening. It keeps tripping me up, when I search for words, because it is not see easy to determine which editor is active after a few back and fores.

I assume this is a bug, but my ignorance has tripped me up before. If this is not a bug, may I ask for instructions to fix it, please?

The highlight is no longer blue, but uses the system accent colour.

All the best,
Keith