How are you going about changing it to 512? Are you doing this via an addon, or are you changing it manually in UserSettings.txt? You may have more than one addon that is trying to change it, or maybe you are trying to change it in the txt file and have an addon that is changing it to 71 by mistake. I think I ran into this once with an addon that was overriding my changes and I didn't even know that addon had the ability to modify the LUA memory at the time. I think the culprit addon in my case was RAETIA Infohub. I always change it manually and the addon was also changing it to something else.