Strange thing is, I'm not using Satin.

Mods:
[✔️] [1.16.2]bettermodbutton-1.1.4
[✔️] appleskin-mc1.16-fabric-1.0.11
[✔️] BBOutlineReloaded-2.4-1.16.3-fabric
[✔️] beenfo-1.16.4-fabric0.25.1-1.3
[✔️] Blur-2.0.0-1.16.2+fabric
[✔️] CustomSelectionBox-5.0.2
[✔️] durabilityviewer-1.16.4-fabric0.25.1-1.9
[✔️] easierchests-1.16.4-fabric0.25.1-1.6.2
[✔️] fabric-api-0.28.1+1.16
[✔️] itemscroller-fabric-1.16.4-0.15.0-dev.20201103.183933
[✔️] light-overlay-5.5.4
[✔️] litematica-fabric-1.16.4-0.0.0-dev.20201103.184101
[✔️] malilib-fabric-1.16.4-0.10.0-dev.21+arne.2
[✔️] minihud-fabric-1.16.4-0.19.0-dev.20201103.184029
[✔️] modmenu-1.14.13+build.19
[✔️] now-playing-1.1.4-fat
[✔️] optifabric-1.8.16
[✔️] OptiFine_1.16.4_HD_U_G5
[✔️] rer-2.1.3
[✔️] RoughlyEnoughItems-5.8.8
[✔️] shulkerboxtooltip-2.3.3+1.16.4
[✔️] tweakeroo-fabric-1.16.4-0.10.0-dev.20201110.132827
[✔️] Xaeros_Minimap_20.29.0_Fabric_1.16.4
[✔️] XaerosWorldMap_1.11.4_Fabric_1.16.4

Tried searching up the issue and found threads concerning the always-tesselate-blocks and ambient-occlusion-mode config entries, and tried every combination mentioned to no avail.

Is there something I'm missing?

Duplicate of #107

It's Blur which includes (and uses) Satin to apply its own shader when the game is paused.

Thanks Chocohead :)