What version of the program is being used? Look at the left-bottom corner of the window or the start-up screen.
Close Videopad and restart it without loading anything. Under OPTIONS | DISK tab, Clear Unused Cache Files.
Load the project and see if it still does it.
You might also install the latest. For licensed users upgrades are free for up to six months from purchase date. After that, VP will continue to fully function but a fee will be required in order to register the newest. Retain your old install file and registration info.