Flaps and faulty servos

I recently installed the flaps on my FreeWing CTLS RC plane and to do so I added two extra servos. Because I had them laying around, I put in two cheap digital servos from RC Timer but soon encountered a major problem.
This video demonstrates the fault that appeared in two of the four servos I bought from RC Timer and also demonstrates how useful the little servo tester devices can be if you're trying to work out why things aren't working quite right on your RC plane.
If you've had experiences (good or bad) with the RC Timer servos, post a comment here and share those experiences with others.