issuue with expanded row in ui grid getting refreshed on scroll, added dynamic rows to grid

[preeti088]

i have injected some extra rows to grid dynamicaaly to create grouping title for names like
A
apple
ample
ama
B
ben
bell
where each row is expanding except title rows --
when i have expanded the rows and scroll the grid it refreshes the grid data again and my values in expanded rows gets reset , which is also creating scroll issue in mobile versiona and data reset issue,
please help me i need help urgently

http://plnkr.co/edit/c74CeE7mAB6w7oGnuht0
attached the plunker ... code is there but plunker currently not working