I spent a few hours today trying to find slime with no luck. My base is right next to a swamp and i've never seen on above ground and I hollowed out a 70x50x3 room at level 12 to see if i could find a slime chunk with no luck.
I've also had issues finding magma cubes in the nether as well as wither skeletons at the nether fortress for what its worth. I had to skip the first nether fortress i found because I couldn't find a single blaze or blaze spawner, thankfully the second one had two spawners.
From what I’ve seen about this bug as I’ve been following for months now since the first 2-3 times this happened to me, this happens on all platforms but seems to be specifically happening to realms which i also experienced. Before converting my Xbox one word to realms i spent lots of time with my sons in a blaze spawn room collecting xp and rods using fire portions with no issues. Shortly after migrating the world to realms i started experiencing these insta deaths that also would destroy some pieces of my armor despite having a fire potion and protection IV on most pieces. Since that that time i now snipe blazes with my bow and stay as far away from them as possible and have been able to avoid insta death.
If if you are playing on realms you can restore one of the auto backups they take, it sucks to loose an hour of gameplay, but it beats loosing all your enchanted diamond armor because of a glitch 🙂