Not able to refresh level 10 crops?

Is there a reason why you can't refresh a level 10 crop oasis? With level 9 oasis I have no issues but with level 10 when I try to refresh it goes from level 10 to level 0.

this is the way it is meant to be, in order to keep an oasis at level 10 you cannot resign it. it must be taken by someone else. then retaken by you.

i guess its to create more competition and people will actually want to fight over them and lose them in order to refresh them

Yeah, what he said ^^^