for some reasons, I can’t generate a file on the PG (it blocks at step “TWO”, but locally, it works, so let’s move on).
The second PG has the resulting vertexJSON and has issues loading it because “is not valid JSON”
Is it the base64 encoding messing here ?
The animation will give a false sense of success because it will bypass the vertex texture and run fine.
For your first PG, you should not do await baker.bakeVertexData(animationRanges) but baker.bakeVertexData(animationRanges).then(...) because you will suspend the engine render loop with the former. The problem is that we need the scene to be rendered to make the animations run (the baker relies on AnimationGroup.onEndObservable) - see how it is done in the doc.
In your second PG, you should await response.json(); as response.json(); returns a promise. Also, loadBakedVertexDataFromJSON expects a string. As you already have the right json object, you can use loadBakedVertexDataFromObject instead: