The good news is I added FSminer's 575 to the machines mod and it seems to work just fine, which will tide me over until i figure out what is breaking the D11 :)
And one last update: I am not sure what I did but I basically sat down this evening and re-wrote the entire terrafarm machines xmls and now I have a working D11.
Your guess is as good as mine and I now know my way around the mod a lot better than when I was just a user of it. Have a few more machines to add in but all is good now.
Thank you for your assistance, for what it was worth. I managed to get it sorted in the end. Now, with two very large bulldozers I can really get to work.