Mobs like zombies, drowned and skeletons won't catch fire when they are on a top slab.

Thank you for your report!
We're actually already tracking this issue under MCPE-32822 so I've requested this report be resolved and linked as a duplicate.

If you would like to add a vote and any extra information to the main ticket it would be appreciated.

Please note, you have also raised this report in the Bedrock Dedicated Server project when it actually relates to the Minecraft Bedrock game - which may also explain why you didn't find it when searching.

For issues with the Minecraft Bedrock game, please head over to the Minecraft Bedrock codebase project and make sure the Project field reflects that when logging a report.

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