Rocker adjustment goes off?
 

Put an engine together and checked clearances and then adjusted cam timing. Had turned the engine over several times after setting the lash to 4 thousands.
#1 valve on a 3.0L engine. Heads came back from the machine shop with high speed springs.

Was just going through the checks and discovered it on a recheck of the cam timing. After I readjusted the lash, had to reset the cam timing as it had changed.

Anyone ever had a rocker loosen up for no apparent reason? It had about 1/8" of slop in it.

Are you sure you had the motor at TDC when you first set it? Are you sure you counter held the adjuster as you tightened the nut? Are you sure you had correct tension on the chain? Are you sure you had the feeler gauge installed properly?
These are mechanical pieces... unlike software, things don't happen by themselves :)
Seriously though... did you recheck the other five? Maybe you grabbed one of the timing marks on the pulley instead of TDC. No affiliation, but that's why I use the Stomski digidix on every motor I build now. Stuff happens... good on you for rechecking everything!!!

That is the same thing that I thought. It is mechanical. Yes, to all. That is what surprised me. I had rotated the engine several times and each time it came back to the starting mark on my dial indicator. Both cams were set.
Wondered if it could be in the head setup at the machine shop. Gave up on that one. Never had this happen before.