Unstable connection since mask patch

[vdragon]

What is your Chunk Download Rate and Chunk Cache Size set to? Have a look at the forum topic here:

Engine: Fixing lag with "Chunk Download Rate"

The Chunk Download Rate option limits the number of chunks the game will attempt to download from the server. If the client attempts to download more chunks than your connection bandwidth can support then the game may start to lag. This will often happen when you’re in areas that contain many portals. The Chunk Cache Size (in MB) option limits the size of the chunks cached locally. The more chunks the client can cache the less chunks it will need to re-download from the server when entering wor…

Try following the instructions in the link and see if there are any improvements. Post your results in there as well.