My 301 can be that way , too. What I find helps is to hold the bobbin left hand, with the ( not technical term here) flapper handle thingy horizontal and opened out. If the Bobbin receiver isn't aligned perfectly to accept the bobbin, frustration ensues. Before you pull the old bobbin, check the alignment. If the bobbin case isn't horizontal, put some scrap fabric under the foot. Carefully advance the hand wheel, turning towards you until the bobbin case comes back to horizontal. Then remove the case and bobbin.
My 301 is in the card table, sometimes I think it would be easier to change bobbins if I lifted it out of the table, and movedit to the left edge where I can access and see the bobbin assembly easier. Good luck.