Not sure if this is the "best" way to fix this issue but it's how I do it.
Select your reflection probe then drag the little dots into the wall a bit, so when you are in the room with the probe you don't see any green walls in your room. The green walls should be inside your walls. If you put them flush with the wall that should work but I've had times were I've had to move it into the wall to fix it.
Hope that made sense.

Some leaks I had from lights were only fixed with putting a shadow caulk in between the wall of the new room and the light source.
However your leak looks like it is because of the reflection probe.