Hmmm....
Well, I slid the bobbin post back and forth and tried it a couple times, tried to push it more toward the hand wheel, tried to help it along with my finger.
Have NOT tried to change bobbins...it is securely on the post, no slippage there. I've only got the three (clear) ones that I rotate through...seems like just last month I chucked all the ones that "didn't go with" my machine. Oh, the irony.
The embroidery machine is A Brother 350. Off to google the specs on THAT...