A Hostile Mob farm does not spawn Zombies when roofed.

"I built the old style minecraft hostile mob farm in the latest beta version of minecraft. After building it, it everything seems pretty fine, but one thing I noticed after being afk in one hour, I dont get any Zombie related drops. Hoping that you can fix this bug in the upcoming original release of the Minecraft bedrock: Nether Update."

"Below are the screenshots of the issue. Two different farms but neither of them spawns zombies."