I play on a Pixel 2, and the Minecraft version is 1.0.7.13.

This ocurrs on my survival world, hard difficulty, no cheats enabled.

I built a 3 Chunk slime farm, based off slime chunk data from https://depressed-pho.github.io/slime-finder-pe/#0,0

I'm using the 3 chunks at 530 147. After extensive cave lighting I got my farm working wonderfully. I was up to my eyeballs in slime balls.

I then built a general mob spawner at 525 180 chunk, and both worked well for a while.

Now all of a sudden 0 slimes spawn in my slime farm, and they keep spawning in my other farm, which is not a slime chunk!