select method of range class failed (sometimes)

[vba_php]

hey you experts,

got another problem with the same files I've posted about 3 times now. sometimes this code breaks with the error ""select method of range class failed"":

With wsDrawings
    LR1 = .Cells(.Rows.Count, 1).End(xlUp).Row
    .Columns("O:O").Insert Shift:=xlToRight, CopyOrigin:=xlFormatFromLeftOrAbove
    .Range("O2").FormulaR1C1 = "=IF(ISBLANK(RC[-3]),RC[-1],RC[-3])"
    .Range("O2").Copy
    .Range("O2:" & "O" & CStr(LR1)).Select
    ActiveSheet.Paste
    Application.CutCopyMode = False
End With

and sometimes it doesn't. image 1 below shows one run where it actually DID work, broken one line after the offending line that sometimes throw the err. the second image shows that instance worked fine. other than me not killing Excel to dump all the memory before every test run, why would excel do this sometimes and sometimes not?