Hey
Let me answer this to all.
X9 & X10 can read and run everything from the .Fpe but when you put a complete file of X10(.X-.Fpi-.Fpe-...)into X9 directory because X9 is older it can't read some info from .Fpe and because of that it ignore the extra info but X10 can't ignore because in X10 the info aren't extra in fact they are needed info.
You can try it in X9 like this
pen the .Fpe files and erase some of needed lines then you can see the same error in it.
Something you can do to solve this is typing new .Fpe for each model or add needed info.
But if you can't do that just do something like this :For example you have a crate in X9 then copy all files into your X10 directory except the .Fpe file and as you know we have another crate-f in X10(Sci-fi from entitybank)then just copy the .Fpe from X10 to your file and change the address file to where your crate is.
Just for near-same models do like this.(Wood-Metal-...)