If you have an old version of the WorkingTitle G3X mod installed, you get that exact error you pointed out. It can actually clash with both the default and WT G1000 as well. As good as it can be, if you ahve it installed, get rid of it. The WT G3X hasn’t been updated in ages and there’s no one actively working on it that I’m aware of.
If you don’t have the G3X mod, then I don’t know what your issue could be.