I have been using Vegas since Version 5 - nearly 15 years or so. I upgrade every other version. Over that time period I have had very few problems and been using Ver 13 for a few years. No problems at all.
I upgraded to Ver. 16 to get into 4K editing. I have not been able to complete a project since installing it. The same projects (these are not even 4K - I am doing some 1080P projects) on the same machine render fine with Ver. 13.
I've contact Magix via email and I am happy to say they have agreed to a refund. My original post was written in great frustration and was not an unbaised account of the issue. I apologize for that. I am sure MAGIX engineers are working hard and in good faith to iron out any problems and I look forward to returning to Vegas in a future iteration.