Currently there’s an error message that shows if there’s an invalid export being fired. However the message is missing some very important information like which resource (and maybe at which line?) is firing this export.
And the error message should be something like
SCRIPT ERROR: CITsave/server.lua:520: is trying to call an export at citgroups (getPlayerGroup) but no such export in this resource.
so CITsave represents the resource that called exports.citgroups:getPlayerGroup(…) and server.lua is the file, 520 is the line.