Mob glitch on Peaceful Mode

Hey I see a issue with the new snap shot or at least it happened when I was using it. I changed the difficulty to peaceful in a super flat world for a map. But I saw slimes glitching blinking and appearing on the screen/world. What I should say to make this better is that the slimes seemed like they were glitching for a second and they were gone and then glitched again on the ground/grass and the difficulty was on PEACEFUL. I don't want to lock it because i may need them in the map but, I just wanted to point out this issue so you guys can fix it. Thanks