I had this problem and after AGES investigating i found an aswer (which will likely be the case for others so i thought I would post).
Essentially, the solution for me was to make sure that my lightmass volume was INSIDE the room where my objects were. if any part of it goes outside the room ,that will add light samples outside (where it may be super bright). if this happens, any object near that sample with have its lighting interpolated and may get made oddly bright as a result…be sure to check for it going below the floor too 
.I hope this helps somebody 
Thanks for the help, @WillSykesGames
I’m wondering how this affects actors in an outdoor area. How does a Lightmass Importance Volume surrounding an outdoor area interpolate lighting with an indoor area inside it too?
The volumetric lightmap is generated by lightmass to handle movable object lighting but by default it is pretty sparse and you will bleed exterior light through walls that are under two meters thick.
This worked for me. I had planes for floors, and light bled through for movable objects. I tightened my lightmass volume, added a giant Unreal cube under the map to block the lower skysphere, rebaked, and that fixed it for me. My lightmass volume still extends just below the floor.
I think the issue might be due to the Lightmap Volumetric Detail Cell Size when you do the Light Baking. For movable objects to light up correctly across the scene, the Detail Cell Size has to be smaller.
You can check the video below to solve the issue.
Hi guys
I have found the true solution.
Just make your object static in editor, bake the lights, and set it back to movable in BLUEPRINT when you need it.
In my case I have done it for my doors and it got fixed after one week of trying every possible way. (UE 5.1)