Was the tension off when you took it to him to fix? It looks like the top tension disks aren't controlling the top tension correctly. That part of this design of tension to me is the weak part of these machines. There is no adjusting it. It looks as if the tension is being let loose every few inches. Yes, you need to call him.

Try re threading and use a test fabric to see when this loose stitching is happening. Make sure you show the repair man your samples.