Extending the drawbridge crashes the game resulting in the following crashlog:

http://pastebin.com/ZeMYDytX

Drawbridge was activated with redstone repeaters in this case, but also crashes with normal redstone powering.

Tested the advanced drawbridge on both a clean Vanilla 1.6.4 version, and a clean Vanilla 1.7.2 world with only Forge, Mantle, Tinkers Construct and Mechworks installed. The Advanced drawbridge can place 3 blocks in 1.6.4, but not in 1.7.2.
Then it crashes with this resulting Chrashlog:

http://pastebin.com/XRtAPBBw

Items in drawbridge?

I got this one as well.

I tried updating Mechworks from 0.1.4.2 to 0.1.6 in my modpack and the client crashes when entering a pre-existing world or server with drawbridges in it.
http://pastebin.com/5QirHXUq

Sorry for the late response, I've been testing it today. Had Railcraft's brick, brick fence and brick slabs in them. This however does not seem to be the cause of the crash.

I tested by taking a single Advanced Drawbridge block and adding one cobblestone to it at a time. Anything three extensions and longer crashes the client upon extending the the third block. Not on retracting, nor does it crash the server. It seems to do the same with any type of block.

The normal and extended drawbridges do not seem to suffer this issue.

Yes, the client crashes when a player tries to connect but the server does not.
I'm using Tinkers' 1.5.5.7 and Mechworks 0.1.4.2 for now and it seems to work fine.

Is it possible there's another mod clogging this up, or are you just using TiC and TMech?

There is a whole list of mods we're currently using, and in our case it is not related to connecting.

Loooking at the crash log it seems to have to do with the fake player used to simulate the drawbridge. We have opencomputers installed which is the only mod I can say for sure of also uses fake players, but then for their robots.

I have both Opencomputers and ExtraTiC installed.

See if you can pin down the mod.

Given the common denominator I'm guessing Opencomputers, I don't have time to test this today probably, but I'll get back to you as soon as possible.

Thaumcraft, we also use that one.

I have the exact same problem. My client crashes when the third blocks get placed by the advaced drawbridge. I'm usingTMechworks-1.7.2-0.2.7. I don't use either Opencomputers or extratic. I have Thaumcraft installed though.

I got same issue https://gist.github.com/Kilobyte22/55b4b8f624c757dc4143 on my server. It however works with some drawbridges (namely one that faces horizontally. it crashes with one facing downwards. Though, seeing as there seems ti be a solution, can it be that i am still on a stable build where that feature doesn't exist yet? if so, where can i get a dev build?

The error is still exsiting in the latest build, so please fix this somehow.

Still not fixed :/
SlimeKnights/TinkersConstruct#1083

Making drawbridges not update on clients seems to fix the issue for me, but I am not sure if that's a good solution to this problem.