I am sure you have looked in where the bobbin casing goes, and taken your little cleaning brush to it. I am wondering if maybe a small piece of thread maybe came loose with the oiling, and is hung somewhere?.. I have a little vacuum that I can use, maybe try that, too...I also had a little too much oil with my last maintenance...and the "grey" thread...I did just like you, ran it without thread, and also with, over and over and over...
Good luck to you,
Kif