Version 1.2.7b for 1.21.5

Using NeoForge 21.5.73-beta

Not using Optifine

Description of the Bug
As shown in the screenshots, modded glass panes that should be rendered as translucent are not. This only occurs if pane_culling_fix is activated in block modifiers.

Steps to Reproduce
I've attached a mod. Try placing down any "leaded glass" (there's a creative tab). It should render as opaque: be sure to place enough to activate the pane culling fix, a 3x3 should do it. Then try placing down any "framed glass": those don't use the pane culling fix, and should render as translucent.
GufyBlocks-1.21.5-2.2.1.zip

Screenshots
Without pane culling fix:

WITH pane culling fix:

Missed overwriting the #getRenderType and #ambientOcclusion methods from NeoForge's API for the pane_culling_fix model.
It should be fixed now in Fusion version 1.2.8.
Thank you for reporting the issue!