Can't create PO prefix and suffix

In testing environment
Go to Settings>Orders>Purchase order number
Add a prefix and a suffix
Click save
Remove a prefix or suffix by clicking the corresponding "x"

Expected behavior: The prefix will be removed from the field but not completely removed from the list of prefixes/suffixes

Actual behavior: when using the x or deselecting in the dropdown the pref or suf is completely removed from the list.