This bug (https://bugs.mojang.com/browse/MC-160464) is still present in 19w40a... All posts seem to show it as resolved as far back as 19w37a but it was not. I had to manually go into EVERY world today (10-7-2019), open to LAN, enable cheats, and set all of these:
/gamerule drowningDamage = true
/gamerule fallDamage = true
/gamerule fireDamage = true
/gamerule doInsomnia = true
They were all changed to false in update 19w36a and NEVER resolved in 19w37a or subsequent versions. I just had to fix it myself.
I didn't want to enable cheats but I had no choice in order to fix all of the worlds created prior to snapshot 19w36a.
Those gamerules were set to false in 19w36a due to a bug, which has been fixed. Therefore, worlds opened in 19w36a are broken and need to be fixed manually. Things like this are to be expected in snapshots.