Thank you very much for your guidelines and notes.
Yes my code has some useless code, it's because I oversimplifed a much heavier code.
thank you anyway for the other tips.
I've been searching and already read the suggested forum threads, but none of the workarounds works for me.
SVG is where I come from for this animation, and GSAP is much easier for controling animations . Anyway I have a major Safari bug with SVG
so SVG is a dead-end.
Ok thank you for trying, that's at least not something obvious I missed.
Will keep trying to get things ok and I'll post the result here.
Cheers !