I have 6 301s. I would rather piece on a 301 than any of my modern,expensive machines. To be honest, you CANT screw up the timing or break them. Nothing but tension to adjust. You may have a bad bobbin. Do you know someone with a featherweight that could loan you a vintage bobbin to try. The bobbins need to come from sewclassic or a good source,not Joann's. Play with your top tension and see if that helps your birds nests. The manuals are all online,if I can work on them, you can too. Just use your camera to take photos and put screws and pieces in a safe place, like a magnetic bowl.
PS the bobbins are interchangeable with featherweights but the presser feet are not!