Blanks keep disappearing in dropdown

I know how to make dropdown menus and how to make the first selection appear as a blank. But I think there is a weird bug because after I do my own thing for a while a come back to change the dropdown, the blank will sometimes just disappear. For example if I have the following cells names Fruit:

[blank]
Apples
Oranges
Grapes

and I enter data validation, make a list with the formula =Fruit
At first the blank will appear, but give it a while and the first entry will be Apples. I can fix it by going to my list and entering something in the [blank] and then deleting it, but it should be unneccessary to "fix" this each time it is acting up.
Either I am doing something wrong, or there is a bug in the program that someone really should have noticed by now. Has anyone else noticed this?