Incorrect normals on flat tiles adjoining triangles lowered from ceiling

[MatieTR]

Flat floor tiles with ceiling geometry lowered onto them do not light up properly unless the floor tiles are broken into triangles. TRNG version works as intended, TEN version has unlit tiles.

Video: https://youtu.be/q2pVF3GFJ5w

Example project: https://www.dropbox.com/scl/fi/sw4sq1qusimmaijgdhkwd/Floor-tile-example.zip?rlkey=exbtazwcck73l1i200onqyeft&dl=0