GoSew

Long time lurker here - and I've learned so much. Now I need !!

I have a Pfaff Expression 2048. Every time I do a test sew - my tension is off and I can pull the stitchs out easily. I have rethreaded too many times to count - step by step correctly. I've changed the needle, changed the bobbin, changed the thread - still not working. Also cleaned out any lint. That noise you hear somewhere in space is my frustration.

Any ideas why this is happening? What am I missing - or does my machine need repair.