Hi
I also have encountered this bug.
My latest save prior to downloading patch 3 was the cr�che, where I had none of this input lag.
Once I travelled back from the cr�che, the lag kicks in due the statues glitching as identified by OP.
However, once you leave act 1, either through the mountain pass or via the grymforge, the lag ceases, so it is only an act 1 issue.
I have tested this as leaving directly from the cr�che to act 2 (i.e. before the lag ever starts) and by going back to the underdark and then going to moonrise (i.e. once the lag is present).
If you are near the end of act 1, the best solution is to just move onto act 2, until this is patched.
