I suspect that the issue originates from how the DOM is re-rendered each time an element is added, causing the animation to restart
Using appendChild of a newly created div instead of concatanating as a string seems to do the trick
KrOW Burey I think you're both on the right track.
I hadn't thought this all the way through before, but there was a 3D Sphere code here that I optimized by converting the 100's of text injections to 100's of objects instead. IIRC, it really helped its load time and this feels like why.