Hey, thanks for the replies (and for GSAP itself too!)
Yep, sure, Vue, agree on everything, it was a sort of minimal example replicating the issue and unfortunately seems to steered the original question
I was just wondering if maybe anyone had any insight from GSAP's side of things, what interaction might be happening between the Tween and the Timeline since separated (by time or code) there are no issues observed with no changes in the Vue-related code that fails once the events are happening concurrently. (Only when the Tween is running it somehow interacts with the assignment of the Timeline object, as the codepen shows, otherwise no issues observed)
I'll likely look into the issue further just for the fun of it, but the workaround of assigning a placeholder "new TimelineMax()" to the Vue's data at start and then replacing it with the real deal is working without any issues for my case, and at worst, I won't be using Vue's data for these objects, no problem. This is likely also a good clue to start the investigation I guess!
Thanks again, will update you if I find out anything!