how come my undo feature shows a bunch of undo threshold options before getting to my last function?

For a few weeks now, when I hit command Z in logic pro x, nothing happens. For example, say I split a region. I hit command Z and the region remains split. I go into "edit" and the undo process shows, "undo threshold 6". So I click it. Then I keeps cycling through "undo threshold 5" etc. Until I finally get to "undo split region". What on earth is going on?