Shadows cast onto beacons are solid black in deferred rendering

Steps to Reproduce:

1. Import any resource pack with PBR capabilities;
2. Enable the experimental toggle for Render Dragon features;
3. Switch rendering mode to "Deferred Technical Preview";
4. Place down a beacon and put anything in front of it.

Observed Results:
The beacon turns completely black.

Expected Results:
The beacon gets darkened a little, similar to other blocks.

Screenshots/Videos attached: Yes

Notes: In the default settings, there's a brief period after sunset in which the beacon gets shaded properly.