To aid in the explanation of this bug i made a video:

Basically what is happening is sometimes when a fog reviling object gets put down on the table (around 50% of the time, it appears to be random when it happens) the game incorrectly marks the area behind a wall placed on the table as seen, interestingly any objects behind the wall itself are not seen (unless the wall is low enough to see the object over the wall, as demonstrated in the video), i also demonstrate how if the wall is locked and clipped into the table this prevents bug from happening.

My uninformed assumption is that the game thinks the fog reviling object is slightly lower then the wall due to a clipping/rounding issue and can 'see' under the wall, anyway i should probably leave the debugging to you

As a side note the edge of the fog of war area displays as being seen (if it has been explored) on the opposite side of the fog of war as seen here:
Bug example.jpg
It's easier to see in the video as it's moving, Also technically this is a separate bug to the one stated above but i figured i'd mention it here as it fits the title and i don't want to make a third bug report today, besides it might not be worth fixing anyway because it's such a minor issue.

and incase it's important:
I'm running Windows 10
My Game version is v11.0.1