yeah no doubt they are buggy as shit. I had them glitching through floors so I cleared out the chunk they were in from Y4 (first level I hit admin ore) to about Y20 to see if that would help the glitching. It kinda-sorta helped. For sure not great but it's slightly better.
Using water seems to help a LITTLE bit too as it seems to keep them from jumping as easily. The little bastards CAN climb ladders so you have to watch for that.
The biggest problem with them is their collision check, they apparently don't go through the check like the other mobs. This makes them able to spawn inside blocks or other areas too small for them. So I guess what happens is a large slime spawns into an area too small for it, it "suffocates", dies and splits into smaller glitchy slimes.
I ran into a room of about 20 of them last night, took me 4 trips to kill them all due to the glitching and having to /home