The question of the Castle BEC has come up recently...
The other possible culprit may be in the Spektrum.

The servo lagging is usually an under volt/amp problem.

Spektrum receivers like constant voltage.
If you have a high draw servo (the Ko 2367 isn't slow or weak), & a weak BEC (Castle) the Spektrum receiver drops.
Do you have a different brand ESC to try or an external receiver pack.

Spektrum receivers may be sensitive to something going on with this, a friends Spektrum receiver has also died shortly after a similar setup.
I don't know the layout on the boards of Spektrum receivers for any internal regulation or limiters...

Castle states there isn't a wide spread problem at this point, but that they have had reports, but "didn't have any servos on hand" that would cause this situation.
I would speculate if you had a an external 5.5/6volt 3+amp BEC the system might be fine.
Only my old 1amp BEC Novak ESC's would do this type of stuff...

Here is an example of a high draw servo & insufficient supply.
http://www.rctech.net/forum/radio-el...bms-617-a.html