Great, can't wait for that to be released to Realms then.
Yup, confirmed it seems to happen when exit/re-enter world while they are active. I 'believe' that it also occurs when going to/from nether.
Same issue in bedrock (Windows 10) - https://bugs.mojang.com/browse/MCPE-33810. Attached a video that shows the issue 'in action'
[media]
I was about to build a slime farm so found this a bit worrying!
However, I seem to be seeing a decent amount of slimes.
I've uploaded a video
[media]of the slimes spawning in my chunks.
Steps taken
Downloaded a copy of my realms world and opened in creative.
Used [MCPE_viz|https://github.com/Plethora777/mcpe_viz] to find slime chunks (I've found 3 in an L shape).
Used /fill to clear all the way to bedrock (a 2x2 chunk square).
Used /fill to create some spawning platforms made out of lit pumpkins
Used /kill [type=!slime] to clear out all other entities (repeated a few times)
Moved > 24 blocks away to allow spawning
I'm using Windows 10, 1.4.2 on Realms