userform misses data when inventory input

hi
this inventory program works up to a point,frmissued collects from a couple of sheets1 and 2 and writes to another sheet3,frmret collects its data from sheet3
and also adds data, all is saved to sheet3 where it is combined and posted to sheet4 if all boxes are full,my problem is frmret sometimes as you click comboboxes does not pick up some data so leaves boxes empty,for the life of me do not no why have tried all different code,for some reason misses a line and it not always the same one,have tried all day with no success at all ,can anyone help please,also use conditional for matting to look for duplicates before it posts them as one row to sheet4,is there code to combine as would like to have location from and location to ,frmret is location to but overwrites the first,any help guidance would be good
please
start frmissued enter name,location,click comboboxes in turn and then each command button in order,
start frm ret enter name location is set,click each combobox in turn this is where it misses some data,
click each command button to right them command 10,all boxes that are full will be posted to sheet4
cheers colin
cheers colin