I checked out ...
https://github.com/solus-project/budgie-desktop/issues/1249
... and tried the "budgie-panel --replace" and got the following ...
brian@macmini:$ budgie-panel --replace
(budgie-panel:11961): Gtk-WARNING **: 13:27:12.855: Theme directory 48/mimetypes of theme Qogir-dark has no size field
(budgie-panel:11961): Gtk-WARNING **: 13:27:12.855: Theme directory 48@2x/mimetypes of theme Qogir-dark has no size field
** Message: 13:27:12.909: libsession.vala:50: DESKTOP_AUTOSTART_ID not set, session registration may be broken (not running budgie-desktop?)
C
brian@macmini:$ budgie-panel --replace &
[1] 11979
brian@macmini:$
(budgie-panel:11979): Gtk-WARNING **: 13:27:44.115: Theme directory 48/mimetypes of theme Qogir-dark has no size field
(budgie-panel:11979): Gtk-WARNING **: 13:27:44.115: Theme directory 48@2x/mimetypes of theme Qogir-dark has no size field
** Message: 13:27:44.165: libsession.vala:50: DESKTOP_AUTOSTART_ID not set, session registration may be broken (not running budgie-desktop?)
... which worked for me (once I had remembered to add the &!) however obviously not a permanent fix
BJA