When updating from 4.7 to 4.7.1 I noticed that dropping items was no longer possible, and moving items around in the inventory was also not possible. With just geckolib there was no issue so I attempted to find which mod was causing an issue when used along side it. However I instead found there was no single mod causing the issue but instead the severity of the lag caused was instead tied to the number of mods included. In a smaller set of mods (around 50) the lag was noticeable but bearable, with a larger pack this issue becomes worse scaling with the number of mods. Going back to 4.7 this issue disappears entirely.

Great, can you do a spark profile for me pls lol

Can you do a spark profile for me?

I can't see anything that would be causing this...

https://www.curseforge.com/minecraft/mc-mods/spark

I've just duplicated the bug while performance testing on the dev version of my relatively large modpack: https://www.curseforge.com/minecraft/modpacks/au-naturel and came here to see if it was already reported.

4.7 gives a tps of ~10ms.

Upgraded to 4.7.1 (and only this mod upgraded) saw tps rise to ~50ms.

Downgraded only Geckolib back down to 4.7 and tps is back at ~10ms.

Likely #698.

I'm gonna close this as a duplicate since no-one wants to provide any actual reports, I'll just assume it's from 698