When a world gets converted to 19w36a the Gamerules firedamage, drowningdamage and falldamage are automatically turned to false, while their normal state should be true.
My world was generated in 1.14.4 but converted to 19w36a from the previous snapshot.
Did not encounter this issue when generating a new world in 19w36a.
Thank you for your report!
We're actually already tracking this issue in MC-160464, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.
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