Is not that they are sending anything worng, it that the CM doesn't like the LLC IE as you noted. It is a perfectly legal IE by the way, sometime present when the call comes from a cellphone or via a transit network.
The IE cannot be filtered. Either upgrade or fix the CM to accept it (I sorry, I don't really know how), or configure the GW for H.323 and it would have no problem in receiving the LLC IE.
These are the paths to get to each CCX logs through CLI. They may be helpful if you are having issues accessing RTMT or downloading logs through it.
If you want to download them you have to prefix "file get " and you can add one of the options (re...