Media Encoder 15.4 - A new issue

Hi Community.

Here is a new one for media encoder.

We render TIFF, PNG or TGA streams to from AE with alpha channels...a lot.  Daily animations for studio use live to broadcast TV.

We have up until the new version, used Media Encoder to compile these stills with ALPHA (usually PNG files) to a third paty codec that works wiht our live studio VIZrt system:

Matrox MPEG 2 I-frame HD+Alpha.  It's been rock solid and fast.

The new version of media encoder corrupts the entire AVI file.  Glitches, Alpha, everything, just goes to garbage, and portions of the image look like they are converted to 16 Colours.

I can pull these same PNG's back into Premiere, or After Effects and they export to this codec fine.  THe problem is unique to Media Encoder.  Any ideas?

And please, before telling me to roll back...no...the previous version of ME was so buggy, the above use was pretty much all we could use it for, as t constantly hung during AE renders.