VEGAS Pro 15 Update 4 (build 321) has been released. Please give us your feedback in this thread.
If you already have build 311 or earlier installed, there is no need to uninstall it. The build 321 will overwrite your installation and retain your settings. Your computer will need to be online for activation after the update.
If you are installing VEGAS Pro 15 for the first time, it is generally better to install using a VEGAS Pro download manager. See here for details & links.
Official announcement with Patch Notes
VEGAS Pro 15 (build 321) installer