My thoughts are a combination of errors
The use of the ARP bolts and the high valve spring pressure (option 2, solid roller pressures).
Even with the bolts torqued to the spec, and the spring pressure being high. The ones that were the looses were the ones in the middle. These are the stand that the oil flows to the shafts.
With the ARP bolts being so smooth and the spring pressure high, they were just being pushed out.
