I fixed the errors in the lines myself on both the default file and on my modded file and then it comes up with this for both
3: 17 cvc-elt.1: Cannot find the declaration of element 'spawnabletypes'.

First error.
Errors in file xml-schema:
875: 9 The string "--" is not permitted within comments.
Second error.
Errors in file xml-schema:
1006: 4 The element type "cargo" must be terminated by the matching end-tag "</cargo>".

The validator I used said there was an error the fisrt error it comes up with is in line 875:9 it says "The string "--" is not permitted with comments. Then once i do what dayz modding community suggest and edit those -- out it comes up with another error saying something to do with the </cargo> is incorrect it says "1006: 4 The element type "cargo" must be terminated by the matching end-tag "</cargo>" it's causing serious errors when editing that make all changes to cargo and attachments load in