Lightmap UV's changes during bake

Hello,

My lightmap UV’s change during light bake is there a reason for that , or is it a bug ?

Im also open for alternative method to avoid dark corners.
I get better corners at default build settings but then everything else looks bad.

Note: All meshes are separate.

before bake

after bake

Result:

My lightmap settings:

Meshes Files:
https://drive.google.com/drive/folders/1L2JQqon_U70AbHT-WZY3Y3iV6rLcHzP1?usp=sharing