Here are some things to consider:
While sewing, be sure the presser foot is engaged and the presser foot tension release is not released.
Be sure the thread is properly fed through the mechanism. One little snag will cause what you are seeing.
Sometimes, I have to disassemble the mechanism that holds the bobbin, clean it all and oil it with a light oil like WD40.
Try a couple pieces of 4 oz nylon (pack cloth), and see how it does. If it will not sew that, try a different type of needle. I find ball ends work best for everything outdoor, but the sharp leather cutting ends can sometimes be needed. I use only Singer needles, others give me problems similar to yours. 100/16 should be an OK needle size for webbing.
If a different needles don't work, adjust thread tension, above, and below if necessary, until the threads above and below the fabric are pulled into the stitch to the same extent; that is, none sticking out or loose on one side after sewing a line of stitching.
Check out your thread. If it is too heavy, like C&C button and carpet, it probably will not work on a home machine. Also, some of the nylon threads sold on spools in gear shops do not sew well, and tend to unravel. C&C Dual Duty Plus is good, and there are even better polyester/cottom weaves in the embroidery shops. Some of the much touted threads break easily. I check how much force it takes to snap the thread before using it - exception, Kevlar, which is very strong.
If none of the above works, I'm stumped. Have an old Kenmore that works much better than a newer "industrial" White I purchased. Beware the cheap discounted imported brands. Singers are good.