Window buttons on panel malfunction

A strange occurrence. I have manjaro xfce installed on 3
desktops. All three have the exact same panels configuration.
All 3 are up to date.
My most used desktop, however, just started something odd.
When I start or reboot the desktop, no started apps show up on
the panel with the ‘Window Buttons’ item.
However, if i right click on any panel and select panel preferences,
then all runnings apps suddenly show on the panel thereafter.
From then on, everything is normal; all started apps show on
the panel. It’s only after a start or reboot that no apps show
until I select ‘panel preferences’.
I even exported the panels from one of the desktops that is
working correctly and imported and applied to the main desktop
to no avail; it didn’t help. Any ideas ?

UPDATE: if I replace the ‘Window Buttons’ item with the
‘Window Menu’ item, the inital “no apps showing when
first starting computer” problem goes away.
However, the ‘Window Menu’ item just shows an icon;
would much prefer the ‘Window Buttons’ item as it
also shows a description.

UPDATE AGAIN: If I go back to the original items arrangement
on the panel, (the ‘Windows Buttons’ item next to the ‘Whisker Menu’ and an expanded ‘separator’ between the ‘Windows Buttons’ and the rest of the panel), the problem remains.
However, if I add another expanded ‘Separator’ between the
‘Whisker Menu’ and the ‘Windows Buttons’, the apps then show
up after first start or reboot.
That works alright, but it displays the apps in the middle of the
panel instead of next to the ‘Whisker Menu’.
I can live with that, but sure would like to know what changed
that it doesn’t work as originally like the other 2 desktops.