There appears to be a crash involved when turning a mob spawner into an agitated mob spawner via PneumaticCraft.

In the referenced issue, a commenter stated:

The simple workaround for this is to disable the "displaySpawnerParticle" option for the "Despawning Spawners" mod.

Crash Log: https://pastebin.com/eEmF1txK

Reference: DarkPacks/SevTech-Ages#1841

This should be fixed in PNC:R v0.6.2, just released (we create a fake player to fool the spawner into spawning when no player is near, but it didn't have a valid connection field so Despawning Spawner's particle effects threw an exception).

Cool!