Lars, 

I think I found the problem: there are references to
font-lock-reference-face in external packages!

In my case, here is one that I use a lot: folding-mode.el

grep there says:
We really need some kind of backward compatible alias --- am sure
folding isn't the only external package that references that
reference-face


grep font-lock-reference *.el
folding.el:(defcustom folding-font-lock-begin-mark 'font-lock-reference-face
folding.el:(defcustom folding-font-lock-end-mark 'font-lock-reference-face
09:54:45 folding-20220110.1718 $ 
-- 

Thanks,

--Raman(I Search, I Find, I Misplace, I Research)
♈ Id: kg:/m/0285kf1  🦮