DMEE - Why copying a standard to bespoke DMEE tree will give different output?

I was faced with this question yesterday and it seems that few payment DMEEs will result in different output when copied into a bespoke Z* or Y* tree. Found out that some of these DMEEs have BADI implemented for them and changing the final file output according to the specific DMEE tree. So, for those who're looking for a reason why your bespoke output file doesn't match the original, do check those available BADI under *DMEE*.

Example that I did yesterday was a copied version of DK_PAYMUL_DOMESTIC. The final file has UNA header as UNA:+,? '. As much as I tried to put a constant in the DMEE tree on a bespoke copy, it won't get copied over to the output file. Found out that there is BADI implemented for that particular DMEE tree, under DMEE_BADI_01 with implementation name DMEE_DK_BADI_01. Copied that and add my bespoke DMEE into the filter and wallah, the output file matches the original.

Hope the above helps those who're stuck wondering why your bespoke copied version won't give the same output result as the standard one.