What is your build date? 12/4 or the hotfix of 12/6?
I just tried using the 12/4 build date and it works for me; however, i've not yet tried the 12/6 build.
If the Position Children in the panel layer is set to absolute, you need to make sure you resize the panel layer big enough to drag the grid inside OR change the Position Children to 'floating'.
UPDATE: I can confirm it works in the 12/6 build also.
Layout grids were not designed to be used inside a panel layer.
A Layout grid should either be a direct child of the page or another layout grid.
A layout grid is a flexible/ fluid container.
A layer is an absolute/ fixed container.
If something works difference than in previous versions then please prepare a demo project so I can see exactly what you have done.
Also, what is your previous version?
After all my problem was not with the layer, just like you said if i configure the layer to position children floating it works like before.
The problem it's other that i expossed in another threed.