I use pixi-spine plugin that uses spine-ts lib.
I have a bug with squashing mesh attachments when try to change animation state. it reproduced with

animations made with spine v3.8.99
pixi.js: 6.0.2
pixi-spine: >= 2.1.10

I have found source of the bug and opened PR on git repo.
EsotericSoftware/spine-runtimes1881
It would be grate if you will watch it.

You can see reality and expectation on gifs below.