General Description

I used the following command inside a command block in repeat mode:

summon minecraft:axolotl ~2 ~ ~ {Age: -100000,Variant: -1}

When I placed a redstone block next to the command block I noticed a slowdown in the world and looking at the graphs in the F3 menu, I saw a massive spike in the TPS. When the redstone block was removed, I noticed the graph 'catching up' and afterwards everything returned to normal. Screenshots and a screen recording of this occurrence are attached*.

I later changed the command to make the NBT valid again:

summon minecraft:axolotl ~2 ~ ~ {Age: -100000,Variant:2}

This worked as expected: after placing the redstone block, a lot of Axolotls spawned, all of variant 2, and no lag was to be observed in both the world en the TPS graph.

Steps to reproduce

1. Place a command block in the world
2. Set the command block to repeat mode and insert the following command:

• summon minecraft:axolotl ~2 ~ ~ {Age: -100000,Variant: -1}

       3. Activate the command block

*Video is encoded using libx265, in case you're having trouble loading the file