If i start playing the scene (unfreezing time, not camerapath), while the time cursor is at the end of the bar, it will start loading like if i wanted to got back in time, but will never proceed (waited 1h) I use Fabric 1.16.4 with optifine and chocapic13 v8 ultra shader
My hardware is:
AMD Ryzen 3800X @4.4GHz
Gigabyte NVidia RTX 2070 SUPER @2.05Ghz
16GB Corsair 3200MHz CL 13 RAM
Minecraft & the OS are installed on a Sata SSD

Also it is fkin slow to change time backwards (2minutes -_-)

Any thoughts ?

Thx for the fast anwser, i'll try it without optifine to see if anything changes (optinfine version: Optifine 1.16.4_HD_U_G6_pre1).
I'll also try Quick Mode, when i saw the name i thought it was made to make the replay faster.

Thx, i'll be sending info about my tests when i get this done.

Does that also happen without Optifine?

Also it is fkin slow to change time backwards (2minutes -_-)

That's normal. We cannot go backwards, only forwards. So, to go backwards we have to restart and go through the whole replay up to the point where you want to go.
I suggest you use Quick Mode while editing, it can go backwards in exchange for replay fidelity (e.g. no armor, no outer skin layers, no particles, etc. etc.).

Ok so i tested out the Quick Mode and it works waaaay better now, thx, but i have issues where is see block breaking particles in the rendered scene.
For the backwards issue, i looked at a bit of the code (so i'm probably misstaken) but from what i could see you generate the scene by "ticking" through it, i was wondering that instead of reloading the replay, then "ticking" through it to get to the the desired time you could save some "keyframes" in a list, so you could "tick" from them until desired time without starting all over again.

I didn't test without optinfine for now, i'll be testing this out later to see if it fixes the issue