ios - New UITableViewCell not drawing properly -

i have cell defined in storyboard, , have

-(uitableviewcell *)tableview:(uitableview *)tableview cellforrowatindexpath:(nsindexpath *)indexpath {     uitableviewcell *cell = [tableview dequeuereusablecellwithidentifier:@"ttentry" forindexpath:indexpath]; 

which gives me cell, , can configure it, , displays fine.

however, when try add new cell using

[self.tableview insertrowsatindexpaths:[[nsarray alloc] initwithobjects: indexpath, nil] withrowanimation:uitableviewrowanimationautomatic]; 

the result new cell half initialised , half drawn. when select cell, rest draws, of uninitialised.

it feels storyboard hasn't completed creating ui objects cell time returns cell dequeuereusablecellwithidentifier.

i'm assuming i'm doing stupid, i've re-read uitableview manual again, , looked on code, , can think of there race condition happening somehow.

incidentally, failure pattern appears same each time run - second , third cells created way wrong, 4th seems ok doesn't gain focus, 5th fails again , 6th works perfectly.

update 09/06/15 i've continued tried old "comment out , see if works" trick, , i've found lines seem causing problem are:

uilabel *label; label = (uilabel *)[cell viewwithtag:1]; label.text = [nsstring stringwithformat:@"%d", numerator[indexpath.row]]; 

within tableview:cellforrowatindexpath method.

so seems it's not happy updating label text @ point, shame since label no without being updated.

should updating label work in method, or using wrong type of view?