Fill horizontally / vertically does not work on 4.18

One of my main machines is running Mint XFCE, recently updated to 21.1 which came with XFCE 4.18.
The fill horizontally / vertically commands stopped working.
Yesterday i tested a fresh Debian XFCE install (also 4.18), and filling didn't work either.
On Xubuntu with 4.16 the commands still work.