This line consistently fails until I manually open the Collections panel once.
/click MountJournalSummonRandomFavoriteButton
I’ve tested a few different ways. It fails when I type into a chat line by hand. It also fails if I copy/paste it into chat. It also fails when I create a macro and place it on my action bars and click the macro. I repeat this again and again and it always fails. UNTIL, I open the Collections panel. Once I open any single tab of the Collection panel (pets, mounts, appearances, etc), then “/click MountJournalSummonRandomFavoriteButton” will work forever more (until I log out).