I had a filter on a relocator attached to a chest which visually disappeared. When I right clicked on the part of the relocator where the filter was supposed to be, my world crashed.

Here is my log file, only the last 10% of it is the crash, but the rest is included for completeness.

http://pastebin.com/tZWYyEuL

Further update: upon reentering the world, the filter was still visually missing (but working). I broke the containing relocator and both the filter and the relocator popped out and into my inventory.

When the crash occured, it seemed to create some sort of weird crushed ore (I'm using relocators to transition between chest >> IC2 macerator x4 >> buffer chest >> IC2 electric furnace x4 >> chest) in the buffer chest that wouldn't smelt.

Please let me know if you need any more information.

Looking at the crash log, it seems like the relocator tile entity did not have a module at that side, which seems to coincide with you not seeing it.

In testing (and I think @Dynious has also noticed this) it seems that this happens not only in your case. Have you noticed relocator modules "vanishing" fairly often?

Well, I'm not a very heavy user of modules as my current setups are fairly simple (mainly just distribution networks), but I can recall one other instance (in my test lab world this time) when a module vanished. I believe it was a blocked extractor module pulling from a normal chest.

I didn't try to interact with it that time, I simply broke the chest and watched the module fall out.

Hmm, I see. I think I have experienced this a few times myself, seems to be a client-server desync. Perhaps @Dynious will have more insight into how to resolve this.

So, this was very hard to find, but I found the problem in the end!

This would only occur with FMP installed. A method onBlocksChanged() in TileRelocator could change the installed modules in some cases and should only be called server side. Somewhere in the FMP code (onPartChanged()) there was a possibility that this method would be called client side, which could cause this issue.

This has now been fixed and the desync should no longer occur in 1.0.6b+!

I have experienced this as well and I'm able to reproduce this bug consistently. This is with FMP ENABLED (will also try this without FMP).

For some reason not all modules are added on the client side (they do remain present server side) after reloading the world (maybe also chuck?). I will investigate this, but I have no idea (yet) what can cause this as some Relocators send it perfectly fine and others don't.