dd15 valve chatter, faulty heads?

hey ya'll,
im posting this just out of curiosity, recently in our shop we've had a lot of dd15 engines have a lot of valve chatter and upon opening the top the intake valves always seem to be too tight, the sound goes away after adjustment but just 5,000 miles later the truck is back with it, they tighten up back and its almost gettin to the point of no more adjusting screw left, always seems to be on the intake valves, this isnt just one instance, we've been having a lot of customers come in with this problem recurring, just a couple days ago i noticed one engine sounded as if one or two pistons were completely off the same noise you'd get from a cylinder cutout kinda like a heavy piston along with valve chatter, took off the top and sure enough the intake valves were too tight and the sound was possibly one stuck open slightly, does anyone know if these heads are faulty or am i the only one going thru this, its all different trucks? throw ur opinions and experiences out here, thanks!

 

id say 2011 to 2013, but i dont remember exactly but i know two of em were 2012's

 

just line haul, far as know dry van

 

was it a recall or something? do you know where i could get more info?

 

sure thing, thanks!