When a silverfish is in a world that's switched to peaceful, the entity still appears clientside, spazzing. I attached a video of this weird behavior, along with a crash report, which seems to not help at all. But, it lists the spazzing endermite as a entity, which might have got the MPServer confused, creating this bug.

Step 1.
Spawn some endermites and silverfish

Step 2.
Switch to peaceful

Now notice how they are still present in their clientside form.