[Shader] at_velocity broken in 1.20.6

[GeForceLegend]

Description of Issue

at_velocity does not working correctly on Optifine 1.20.6, causing visual artifacts on entities when shader is using at_velocity to calculate motion vector. It works fine on 1.20.1 I6.

Steps to Reproduce

1. Using shaderpack SEUS PTGI HRR3 with Optifine 1.20.6
2. Join a world and moving, and see if entities get extremely blur

OptiFine Version

1.20.6 I9 Pre1

Installation Method

Standalone

F3 Debug Screenshot

[GeForceLegend]

Still exists in 1.21 Pre8. Hope it can get fixed before stable release of Optifine 1.21.

[sp614x]

Probably fixed with #7714

[GeForceLegend]

Tested with HRR3 and still not get fixed, this started happen on 1.20.6 (not sure if 1.20.4 also affected), so might be nothing related to wrong at_midBlock that only exist on 1.21 previews

[sp614x]

Fixed, coming in next preview.