How to stop lag in Magix Vegas in one step

Forget all the other obvious solutions (preview quality, device on and off, etc). This solution works beautifully on my low-end laptop and on my super desktop,

1) Go to options and click shift key and preferences at the same time.
2) Open "Internal" tab.
3) At the bottom look for "enable multi stream render".
4) Change value to "TRUE".
5) Restart Vegas.