Hi pete,
Thanks for digging into it. Your conclusion about the menu reroll interaction is correct, and M&U is looking into it.
However, let's throw another extension into the mix:
Advanced Effects, which lets me prepopulate effects on the NPC sheet before it lands on the CT. When I use this and set FIXINIT for a NPC (such as a lair action NPC always locked at 20), and drop the record onto the CT, the order is correct but the displayed number is incorrect only when this spell damage extension is included as well.
Attachment 54788