Actually it was Pioneer factory people in LA working with a dealer who owned the display. Not your typical folks. They were about to swap the set out.
The problem is this problem is not easy to reproduce with your normal test material. It is a function of source quality. Perfect sources do not show a problem while highly compressed ones have huge problems. Compression can cause problems if the logic switches modes too quickly. Anyone will have trouble reproducing this without extensive use with various quality material. Various test and reference sources are not useful for this.