Media Encoder 15.2 error code 5

I had to downgrade back to 15.1 due to an MXF importer error running 15.2.  The error occurs when attempting to export H.264 from a sequence built with a variety of source files: MXF, APR 422, H.265, H.264 and a variety of LUTs.  This is a typical assortment for my workflow so I downgraded.  I tested several successful workarounds in 15.2 -- 1. disabling hardware encoding and 2. exporting partial sequences with only MXF clips.  MacPro7,1 / MacOS 11.3.1 /  AMD Radeon Pro Vega II