While working on an uberminer in the Direwolf20 pack (1.0.19), I discovered a bug that caused the client of any player near the miner to crash, and spammed the server log with warnings according to the server owner. Unfortunately, I wasn't able to get a copy of the error log (which the owner noted was enough to lock up the server console), but what he mentioned about the errors gave me a theory, which seems to have been proven with testing.

Using a MFFS Force Projector allows you to move a set of blocks, which works as expected. ProjectRed Red Alloy Wire can trigger the force projector, which also works as expected. However, when using two Force Projectors to move each other, connecting Red Alloy Wire directly to the force projectors causes this error spam.

It's worth noting that this error spam can be entirely avoided by simply placing a piece of vanilla redstone between the Red Alloy Wire and the Force Projector. My guess is that Red Alloy Wire is keeping some sort of cache of the state of the block it's connecting to, and the MFFS Force Projectors aren't playing nicely with that. By adding in the redstone, the ProjectRed circuitry doesn't connect to the complex MFFS block, but instead to a simple block with only an on/off state. The redstone doesn't care about the MFFS block state or location in any way, and simply provides signal, so by placing redstone between the Red Alloy Wire and Force Projector, I'm effectively "dumbing down" the ProjectRed circuitry to the point where it plays nicely with MFFS.

This configuration causes the error:

This configuration is error-free:

Sorry about the lighting oddities; the miner was unfortunately built at cloud level.

MFFS doesn't support moving multiparts. This is an issue for calclavia.