It seemed ground:db is not supporting mongo ObjectID?

I found an offline storage test project for Meteor, using meteorhacks:subs-manager and ground:db. the project worked fine, but if I insert some data from server side(using "meteor mongo"), the data cannot be persisted when offline. the only difference between data inserted manually from server side and data from client side by pressing buttons is the _id's format: plain string vs ObjectId(string). And errors occurred like: "Meteor does not currently support objects other than ObjectID as ids".
I am a beginner, I don't know if the reason is ground:db not supporting ObjectID version of _id, or subs-manager. I hope somebody can upgrade the related plugins. Thank you

Start by reproducing offline persistence with records inserted through "meteor mongo" using an ObjectID _id, then compare them with client-created records in the offline storage test project. Trace whether ground:db or meteorhacks:subs-manager rejects the ObjectID and confirm that the issue is resolved by identifying the responsible plugin and its supported behavior.