I purchased this engine for my Avala and Drava formations. It came in DC and found a DCC Sound decoder from the Hungarian brand DigiTools that I ordered from Vasútmodell.
I found that the "extra" piece needed to be glued again by the buffer on the left side.
It wasn't easy to remove the body. I did follow the instructions; there are no screws or pieces to remove; it was just stuck and I had to force a little, but no damage was done!
It took me a while, a long while, to figure out that the decoder was going underneath the main board. It was my mistake since it was actually written in the manual, but looking at the black plug from above, it seemed logical to put on the top rather than removing screws to put it underneath. Anyway ...
Everything works perfectly on this one (different from my PKP EU07). However, I cannot find out how to change the address from 3 to something else ...