hi frailtyman and welcome to the forum! first try to search if your issue wasn’t answered before, you have a same problem as described here: Exporting large animation makes colors go crazy - #4 by mich-spich
long story short: gif supports only 256 colours at once, and when i check your image here: PJ Image Inspector v2.0 i see number of colours being 256 so the reason is that you pushed over the limit of gif format.
export your image to png or - if you need gif file - try to optimize your palette and re-use as much colours as possible.