Summoning a wolf using a command block for example, leads to the wolf glitching inside the command block and turning slightly dark rather than stepping on the command block and moving on.

How to reproduce

Start by obtaining a command block by using the command

/give @a minecraft:command_block

Then summon a wolf using the command block, you will notice that the wolf glitches inside the command block and changes color while suffocating.

Observations: When a wolf is summoned by using a command block, it glitches inside it.
Expectations: It should step on the command block.

Note: When entering the command 

/summon wolf ~ ~1 ~ 

in the command block, it will differ leading to the mob spawning on top of the command block, so if that's the case, summoning a wolf should also spawn the wolf on top of the command block or it maybe intentional.