How to make Save Target As STICK on the ribbon?

I've had this problem before but through most of 2019 it seemed stable. Just upgraded to 2021 and yay, the problem is back. Not matter how many times I add the "Save target as" function to a custom tab/group, it never sticks. And no, it's not overloaded, I've only got 4 items on it.

Any idea what ails 2021 in this regard?