This is the foam quad I created several weeks ago. On the first flight, there were several wobbles, not stable like my other quads have been. I purchased a used flight controller and it could be the f/c needs recalibrating, or it's bad. The wobbles could be from a floppy frame - I added a rigid member to the frame today and that seemed to help quite a bit - it flew with some wobbles but at times it was flying with good stability. I may also need to check the flight control settings on the f/c as well as the settings on my transmitter. Another possibility for the wobbles could be the way the motors are mounted - I don't think they are flexing and I think the shafts are clear from any interference with the motor booms but I'll check that also. I do know I did a thorough job balancing the props so that shouldn't be an issue.
Sooner or later, I'm fairly certain I'll get rid of these wobbles - unless it's just a bad design.