I think the issues are caused by the fact that the light is inside a huge mesh AABB in your test scene. In that case the projected AABB corners are not useful to find the screen space bounds of the geometry, instead the geometry should be recognized as covering the whole screen. Could you please test the attached patch which should fix this problem?
worstplayer wrote:
I'm probably getting incredibly annoying at this point
It is good that you find these issues as they don't show up in our rather simple test cases. So we have to thank you for your help
Please let us know if you find more issues!