The issue with the package.json error there is the following line in node_modules/grpc/src/grpc_extension.js:

var binding_path =
    binary.find(path.resolve(path.join(__dirname, '../package.json')));

where __dirname then has a different meaning in the built file than from the original.

the above binding_path is then passed directly to require. Ideally binding_path should be statically computed in its entitreity.