Joel Lieberman

Looks like 1.2.10 might have a fix for this.

https://minecraft.gamepedia.com/Bedrock_Edition_1.2.10_build_1

"Increased the spawn rate of slimes"

I'm on Windows 10 and have dug out two slime chunks and spent multiple nights in the swamp. After 100 hours of play, only two slimes have spawned.