Can you upload that sample, or a short 5 sec clip with the error to dropbox?
What is the “media info” – https://mediaarea.net/en/MediaInfo on the source video.
What OS and system specs do you have.
Have you disabled the GPU under Options > Preferences > Video > GPU acceleration? Then restart Vegas and test.
Are your GPU and sound drivers fully updated from the manufacturer?
Are all the windows updates applied and your system restarted after any installs?
To me that looks like corrupt video file, an odd codec that vegas is not decoding correctly, or GPU software fail.