Video corruption usually happens when the structural metadata of a file is damaged. Videos are complex containers holding video streams, audio streams, and indexing data (the index tells your media player how to synchronize the sound and images).
Old, cached files are a common culprit for loading errors, as they can conflict with the most recent version of the site.
Finally, if "av4 videos us fix" refers to accessing a website hosted at the domain av4.us , the term "fix" likely means "how to access." However, the site appears to be a redirecting or potentially a placeholder domain.