Well darn, I think Jamo is right...
The issue seems to turn on WHEN the valves got loose. With some suggesting the motor was shipped that way. Seems to me they got loose at some point following initial run in and down the road a bit. Which is to be expected with a new motor. They could have gotten tight, instead of loose. Either way, you got trouble the manufacturer cannot address after shipment.
I recall George Anderson (Gessford Machine) being very adamant about checking and double checking the valve adjustment AND rotation of the lifters before, after and during the run in period. You have to stay on top of it.