Well firstly, I have One Plus 3 Android phone.
The issue is that monster dungeons (although i've only tested one) will spawn mobs even when the room is really well lit.
What i've expected:
Well, since ive claimed the dungeon in the official release, i can go there without worrying that i will be attacked by mobs, due to it being well lit.
What happend:
When walking upon the monster dungeon, i was greeted by 4 skeletons who have just spawned in. This should not happened, due to it being lit.
Steps to reproduce it
1. Set your diffuculty other than peaceful
2. Create a world
3.Find a dungeon(or for the people at Mojang, use the awsome magic of spawning in one.)
4. Claim it by puting torch around the place.
5.If you still have mobs spawning. Congrats it worked
I have provided a YouTube video link for this
https://www.youtube.com/watch?v=Zplk_rm-76o
This just explains what happend, but with no sound 😞
Related issues
Comments

Yes, this has been around the Beta for a while now. They would also spawn inside the walls and floor and proceed to suffocate.
Thank you for your report!
However, this issue has been closed as a Duplicate of MCPE-17114.
It has been linked to this report. If you have additional information, please add it to that report.
Please search before reporting, as it's likely that one exists already.
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Can somebody else confirm this