Hastings Manufacturing Company has published bulletins in the past on glass beads and other pressure blasted cleaning media that is not completely removed before the engine is reassembled.
When engine parts such as heads, intake manifolds, blocks, etc., are pressure blasted with glass beads, steel shot, or various metallic oxides, this material is blasted through all the internal passages of the part. If not thoroughly removed by some reliable cleaning process, the cleaning media will be ingested into the engine's intake or oiling system or both. When this happens, the engine is generally destroyed.
The photo shows glass bead damage to ring sides.
The rings were stuck in the grooves and the engine stopped and could not be restarted due to lack of compression. Since only the pistons and rings were examined we could not evaluate damage to other engine parts, but the engine was rendered inoperable by the glass beads.
Your shop must establish a reliable cleaning process that will completely remove all cleaning media from the engine parts, or expensive engine damage will result.