This only occurs in 4.17 with the forward renderer enabled, tried in 4.15 and 4.16 but the shadow works properly in those versions. Steps to replicate:
Create an empty 4.17 project
Enable Forward Rendering
Create a big static cube, smaller movable cube and stationary point light
Bake lighting
I hope I’m missing some obvious new setting in 4.17, anybody got any idea how to fix this?
After doing some digging I was able to find that this is a known issue. I have provided a link to the public tracker. Please feel free to use the link provided for future updates.