I've used crimson planks to build near a lava pool, and the exact same block have been catching fire about once or twice every Minecraft day. After a few seconds the fire goes out, but I don't think it should have started in the first place. The block below the planks isn't flammable either (stone bricks).
My search for duplicates yielded the same bug for MCPE, but this is Java.
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However, this issue is Invalid.
Your game, launcher or server is modified.
If you can reproduce the issue in a vanilla environment, please recreate the issue.
Any non-standard client/server/launcher build needs to be taken up with the appropriate team, not Mojang.
Any plugin issues need to be addressed to the creator of the plugin or resource pack.
If you have problems on large servers, such as The Hive and Hypixel, please contact them first as they run modified server software.
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