Mobs and events freezing

After maybe 2 minutes of loading into the new snapshot, everything froze. any NPC, mob, redstone objects - but I could still move around. This happened to my already made world that was running the snapshot before. I went into a NEW superflat world with the new snapshot, and this didn't happen. Maybe something happened with the updating of my already played on world. Both worlds were in creative. 

I tried to lower the tick speed after seeing that being a possible solution with pervious snapshots freezing. Didn't work.

When I would go to close out of Minecraft, It wouldn't work and I had to force close it. when the launcher reopened, it said something went wrong.