Wrong calculating of units diff

[Tetraquark]

It looks like sometimes the diff calculation does not work correctly after updating the unit list. A prime example is adding the end of the list the loading unit to display the loading process of the next page of the list. After deleting the loading unit then for all units will be called binding again.

Maybe we can add a callback to calculate the diff or to specify the correct identifier or hash of the unit data outside (or pass a comparator or something).