If the value listed in the capacity field of a Delayer ever becomes 0, Minecraft becomes unresponsive. There are several ways this can happen: Intentionally, by entering "0" into the field, or unintentionally, by editing a value that contains zeros such that at any time the remaining value is 0. Emptying the field and then clicking the increase value button also causes this value to be 0.

This has caused the world to be unloadable at least once for me. To recover, I used MCEdit to delete the problem Delayer.

I'd recommend adjusting it such that any value less than 1 is treated as 1 for this field.

I thought I recently fixed something similar to this, will look into it.