One motor slows down and then stops

Steps to reproduce problem
1.Normal power up procedure
2.Arm system
3.Apply small throttle increments (say up to 10%) - 3 motors spin normally but 
one motor does not (say motor 3)
4. Apply more throttle say 20% and now all motors spin.
5. Maintain at this throttle setting and the motor that did not start normally 
will start slowing down and finally stop. The other 3 motors keep working fine.
6. Add more throttle (say 30%) - motor 3 starts again but then slows down and 
stops

Equal rotation on all four motors - One motor just keeps slowing down and stops

Using Arducopter 2.8.2 on APM1 2560 bought recently
Turnigy Plush 25A ESC set with timings recommended as defaults on the APM site.

This does not appear to be related to the ESC/Motor since if I change the motor 
o/p from the APM the problem moves from one motor to another, always to the one 
connected to the faulty APM o/p

I have seen a post "Motor 1 slows down and stops" which seems to be exactly the 
same problem but there did not seem to be any real response to this thread.

Original issue reported on code.google.com by designst...@gmail.com on 28 Nov 2012 at 9:26

Merged into: #514

Ebeo / arducopter

One motor slows down and then stops #523