• This is a mod incompatibility. If I do this in vanilla Forge with only Et Futurum Requiem installed, it works normally.

Version number of Et-Futurum-Requiem (IMPORTANT)

Et_Futurum_Requiem-2.4.4+nomixin

Describe the issue (IMPORTANT)

Yes, it's a nitpick for all we know, but ugh. It doesn't crash, the issue is that it just doesn't work. We honestly tried to find a workaround, and stumbled here. It says: "Et Futurum Requiem: Fully compatible with the right workarounds. // Crash on startup. Fixed by disabling skin backport (enablePlayerSkinOverlay in functions.cfg). Elytra is incompatible with PlayerAPI. Fixed by using this fork of Smart Moving + PlayerAPI." Sure. Used all the forked stuff. It doesn't crash, so success, but it still doesn't work. It evidently tries to, as we jump it switches the camera a little and we don't receive fall damage, and it sometimes even renders in the inventory screen, but the player still falls straight down.

The issue is fully reproducible with this modlist:
Et_Futurum_Requiem-2.4.4+nomixin.jar
PlayerAPI-1.7.10-1.4.jar
RenderPlayerAPI-1.7.10-1.4.jar
SmartMoving-1.7.10-15.7-maka.jar
SmartRender-1.7.10-2.1.jar
-unimixins-all-1.7.10-0.1.7.jar

I am considering having this issue moved over there.

Looks like I can't, I can only transfer it to repos I own. Oh well

SmartMoving-1.7.10-15.7-maka.jar

That's not the latest version, EFR compat was added after that release, I just haven't made a new release since then. I released SmartMoving 15.8 and PlayerAPI 1.4.1 with the latest changes now.

I am considering having this issue moved over there.

Feel free to move it if you can (I can't for some reason.)

In that case @RaidhoSketch, open a new issue in the Smart Moving repo if the issue still happens with SmartMoving 15.8 + PlayerAPI 1.4.1.