Miguel Pelaez

Hey, I tried to debug this issue. Using the official Minecraft mappings, at the class GameRenderer, the problem seems to be the calling of

this.postEffect.process(float2);

If you disable just the post effect call, everything works. So the surrounding code is not the problem.

RenderSystem.disableBlend();
                RenderSystem.disableDepthTest();
                RenderSystem.disableAlphaTest();
                RenderSystem.enableTexture();
                RenderSystem.matrixMode(5890);
                RenderSystem.pushMatrix();
                RenderSystem.loadIdentity();
                this.postEffect.process(float2);
                RenderSystem.popMatrix();

So the PostPass class is the problem, the process method to be specific.

Confirmed for 1.15.2

This would be a very good fix to do in 1.15 as it's intended as a bug fix update. Incredible work by the community, it fixes almost any redstone lag on my test server.

Same, with 1.13.2 vanilla