That's interesting. The fact that remounting the needle curing the bubbles and now the throttle hunts at low speed suggests you may have a worn needle valve. If the threads are worn or the tip of the needle has unevenness on it you can get the problem you describe. Try just touching the needle with the engine running and see if you get RPM changes. If you do you need a new needle. If the needle seems OK just richen a little. That should cure the hunting.