Conditional Formatting issue

I'm running Excel 2021 on Windows 10 Pro (64-bit).
I seem to be having some form of delay with the application of Conditional Formatting,
where I have to scroll past the cells subject to the formatting, before the effect takes place.

Sheet2 looks like:

I want the conditional formatting to affect any cell in $B$6:$F$91 that matches
any of the numbers entered in $B$2:$F$2 by changing the font color to Red and Bold.

The rules manager shows the following:

If I enter a 4 in $D$2 and press enter, cell $D$6 does not change until I click in the window
outside the sheet, or scroll down so that row 6 disappears at the top of the screen.

Similarly, if I clear the contents of $C$2, the number 03 in row 6 stays red until I scroll
row 6 off the top of the screen.

I don't know if I've missed some important aspect of conditional formatting or
if I've managed to affect some global setting in Excel.

Once I've figured out this problem, I want to display a count of the cells in each row
that were conditionally formatted, a 2 for example in $G$6.
Any help would be appreciated.