When the sun shines through the foliage, a square forms in its place. I'll try to attach a video recording.
https://youtu.be/_H7hT5PU2MA

this is a known issue with screenspace contact shadow's subsurface scattering effect.
for now you can do one of any of these things:

• turn off subsurface scattering in LabPBR settings (this will make plant shading suck)
• turn off screenspace contact shadows (this will disable the far away shadows cast, and fine detail tiny close shadows)
• try to ignore it >:)