Don't need to get your panties in a wod, there just opinions, no need trashing others opinion just because your trying to get your point across.
Could it be the vavletrain, sure it can, but do you realize how much preload would be needed on a hyd. lifter to keep a valve hung open, a good .080", I'm sure the machinest isn't a total idiot that he didn't know it had fixed rocker shafts, the cam isn't that big, so the only way it would start hanging valves is if the heads were milled a ton or the block was decked quit abit.