Animation Playbox / Blame It On Updates

I updated the latest versions of After Effects and Media Encoder (2018 Update) and all my GIFs were buggy when outputted.

(See the strange effect below)

2017:














2018:














(I have no idea where the ‘Blame It On the Boogie’ style trails were coming from?)

(The Jacksons - Blame It On the Boogie

...I spent today trying to figure out what I did wrong, but my settings seemed the same...

Eventually I just reverted back to the 2017 version and the problem was fixed. No sure if this is a GIF bug in 2018 versions of the software...

I’ll try to stick to 2017 for now. Mentioned the problem in the Adobe help forum (first time I've used it).