These machines were not meant to be temperamental, they were meant to be easy to use.
Change that needle and get that machine's timing checked and adjusted on a regular basis, at least once a year, or sooner if it continues to be temperamental.
timing between needle lowest position and bobbin thread/hook rotation completion
and
timing of needle throw from left to right, right to left
These can have a big effect on all stitches especially anything that zigs and zags like decorative stitches.
Most of all, don't forget to have fun!