A dirty shuttle race, improper thread routing or incorrect thread tension can break the bobbin thread.
Unplug the sewing machine and check thread routing according to guidelines in your owner's manual. Reroute the thread correctly if necessary.
Also, check thread tension settings because incorrect thread tension can break the bobbin thread. Set thread tension according to the guidelines in your owner's manual.
Clean the shuttle race because lint and debris buildup can bind up the bobbin and break the bobbin thread.
These repairs may help solve your sewing machine problem
Clean the sewing machine
Clean lint and debris from the shuttle race every 3 months because it often attracts lint and dust. Clean the feed dogs at the same time because they also attract lint and dust. Clean those areas more often when using the sewing machine regularly. Oil the sewing machine after cleaning.
Adjust the sewing machine thread tension
Tight upper thread tension causes skipped stitches. Reduce the upper thread tension when the sewing machine skips stitches. Adjust lower thread tension as necessary to balance with the upper thread tension to create perfect stitches.