So, I went ahead and actually recreated all my model groups with new names and repopulated them. I'm doing general cleanup right now. I fully understand I'll need to re-map when I load my previous sequences.
I've attached my xlights_rgbeffects.xml file. If you look at the allhsenolmgahf1 model it has the model group allflakes in it which also contains model groups allgrflakes and allrfflakes. What I've found is xLights doesn't seem to like double embedding of Model Groups as allflakes does not highlight in the layout though you can clearly see it's added in the XML file.
So maybe I'm just pressing my luck by placing a model group, within a model group and finally...within a model group, but as I said, I'm trying to cleanup my layout and make it a bit more organized so the fewer elements I need to add to each group the cleaner...but maybe I'm hitting a limit

Thanks again!