userform not copying all to sheet

hi
can any one help me with this have gone over and over this till my eyes hurt,and come up with zilch,run scan out (frmissued)/ enter first 3 xes enter different bar codes in first 3 comboboxes, enter 200 location and anything in plant number,click save,all 3 items are sent to sheet3 as should be,
click scan in (frmret)and log in again,enter the same 3 barcodes you scanned out click save,this is the problem all items returned should match the ones issued if they do sheet3 is updated and entried deleted and sent to sheet4,at the minute all are deleted but only 2 are sent to sheet4
,although none are left on sheet3 it looks like it takes all of them off but loses one as its sent to sheet4, can any one put me in the right direction please , this has worked before and I am going through old programs now to see if there is any difference in coding
cheers colin