Not picking up the Bobbin thread

Double check that bobbin thread is correctly threaded through its tensioning path.
If it sews fine when sewing a straight line or zig-zag stitch you might have to loosen off the top thread tension a bit, or tighten the bobbin tension.
There is usually a small screw that controls the bobbin tensioner that can be tightened slightly to adjust bobbin thread tension. Do this little bit at a time and test after each adjustment.
Be careful when adjusting, take clear photos before touching anything so that you can put them back where they were if need be. Good luck.

Not quite sure since the symptoms are not clear. "Bumpy stitches from bobbin"--does that mean there were thread nests on the bobbin side of the fabric? That is thread nesting or bird nesting resulting usually from mis-threading, upper thread not completely seated in tension disk, or upper tension too loose. Remove the upper thread from the machine. ALWAYS RAISE the presser foot and rethread from the beginning--verify the thread path is correct. Set the upper tension to the midway point between high & low number and retest the machine. (Upper tension may need to be tweaked because fabric, thread, and age of the machine will have an affect.)

Check that the bobbin is wound smoothly--no lumps, bumps, or thread ends/pieces sticking out of the bobbin. Check that the bobbin is installed in the bobbin case correctly (turning the proper direction) and the bobbin tension is threaded completely.

If the upper thread is not picking up the bobbin thread, make sure to install a brand new needle. (I don't try to straighten or "fix" damaged needles. With today's computerized machines, it may cause more damage than a new needle would cost. That may work on the old mechanical machines like the Singer Featherweights, but my machines are too important to risk for the price of a needle.) If it still won't pick up the bobbin thread, then the machine's timing has probably been knocked out of alignment. Search for sewing machine timing or take it for service.

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Do you use stabilizer when you are satin stitching? I had a teacher who also hooped the fabric with a spring-loaded embroidery hoop (turned upside-down under the presser foot so the fabric is flat against the needle plate) that would keep the fabric taut.

It is not uncommon for bobbin thread to rise to the top when doing embroidery, satin stitch, etc., especially if you are using lighter-weight thread than usual. You would normally loosen the upper tension so the upper thread will sink into the fabric. However, if loosened upper tension is not doing enough, you may need to adjust bobbin tension when doing embroidery, applique... You might try tightening the bobbin tension just a smidgen to get the bobbin thread to stay below the fabric. Be sure to mark the bobbin case before making any adjustments so you can return it to the original setting when finished with the satin stitch. (If you do a lot of satin stitch or applique, etc., you may want to invest in a separate bobbin case that is set up only for doing that kind of work--saves having to alter the bobbin tension frequently.)

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Sounds like a tension issue. Try rethreading the upper thread first and then lower the upper thread tension.

I agree with sylviaivie about find another repairman, they are suppose
to guarantee the work they do.
when the upper shaft is replaced & then the machine is retimed
the machine should work just fine.
but just don't take it back to that man to be repaired
here is a tip if it happens again,,
always try to cut the top thread first,
& turn the machine up on it's back to access the bottom cover
take the cover off the bottom to get access to the bobbin thread
where you can cut the bobbin thread
then you should be able to get the needle out without breaking it &
damaging the upper shaft, replace the needle & make sure
that the thread is good quality & not knotty, clean out the bobbin area of lint or thread
always change the needle on the embroidery machine every project
make sure the bobbin area is kept clean of lint or thread
clean under the needle plate at least once a week for lint if you
embroidery everyday or just often

With the embroidering, some of the bobbin thread is SUPPOSED to show on the top of your embroidery-the machine isn't doing anything incorrectly. You'll need to thread your bobbin with the same thread as you are using with the top. I had the same "problem" when I first got the machine and took it to a wonderful local technician whose helped me with a lot of things who informed me that this is perfectly normal on embroidery machines.

Re-thread, re-install the bobbin, change to a new needle.

If the problem continues the machine may need to go into the shop for service.

I cleaned the machine good with canned air, oiled it. I took out the bobbin case and cleaned it good also. I then noticed the tension screw on the bobbin case was loose, tightened it and the problem was fixed.

It sounds like the machine needs to be timed, seek out a sewing machine repair shop for this service.

Check the timing.