Slime froze midair

I was in superflat, jumping around and hitting and killing slimes, when suddenly one them, a medium one froze in midair. It doesn't respond to taking damage or anything.

 

When I quit and came back, it died to the lava.

 

I was in creative mode, so I think this can't be a duplicate of MC-134974 

Also, only one of the many slimes froze. All the others kept jumping around.