Suggestions ... that may or may not be your issue but are worth a try.
https://www.nch.com.au/kb/10265.html
Close all other programs when exporting.
What are the specifications of your PC: CPU, free space on the c:\ drive, graphics, RAM?
What version of Videopad is being used?
What is the length of your project, source file type/s, export format and resolution?