Issues exporting existing type

I want to export an already existing Type but there is an issue I can’t get solved.
MakeOTF error: Glyphs_error

I have tried to open the command file, but nothing happens and I have no clue what to do now.

Thanks for the help.

This means you are mixing lookup types that cannot be mixed, e.g. one-to-many with ligature substitutions. Separate them into different lookups and they should work. This is the basic structure of a lookup:

lookup NAME {
# code goes here

Make sure their names are unique.

Did you open an existing OpenType font? Then the decompilation is not 100% possible. Check the feature code and if you can’t make sense if it, deactivated the offending feature for now.