Vulkan Mobile: Lightmaps flicker and unload when there’s more than 2 instances in screen

[SpockBauru]

Tested versions

Reproducible in: 4.4.1.stable and 4.5.dev4

System information

Godot v4.5.dev4 - Windows 11 (build 22631) - Multi-window, 1 monitor - Vulkan (Mobile) - dedicated NVIDIA GeForce RTX 3080 (NVIDIA; 32.0.15.6614) - 12th Gen Intel(R) Core(TM) i7-12700KF (20 threads)

Issue description

When there are more than 2 LightmapGI nodes on the screen, lightmaps start flickering and loading/unloading randomly.

According to the documentation the limit should be 8 instances, which work for both the Compatibility renderer and Forward+ but not for Mobile.

This issue is accompanied by a one line PR that aims to fix it: #106907

lightmap_bug.mp4

Steps to reproduce

Open the MRP and run the game (F5)

Minimal reproduction project (MRP)

lightmap-bug.zip

[clayjohn]

I think this is already fixed by #106748. Did you test it? The fix will be available in 4.5 dev 5

[SpockBauru]

I tested Master today, #106748 does no fix it