What version? Here's 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.
What is the resolution of the bulk of the source files? What are the export settings?
Folks here will be glad to help solve the issue if you share the project. This is easy, quick and can be private. Just follow these steps carefully and we'll take a look...
Back up --- With your project on the timeline, click on MENU at the top-left. Click FILE|BACK UP PROJECT FILES TO FOLDER. Choose a folder and SELECT FOLDER.
Upload --- Upload the saved, numbered FOLDER. Use a free server - Google Drive, MS OneDrive, etc.* Do NOT upload the individual VPJ or export file.
Get link --- Get a public link. If using Google Drive click GET SHAREABLE LINK. Change "restricted" to "anyone with the link can view" Click COPY LINK | DONE.
Share --- Paste that link here, or click the folder at the top-right of this forum to message it privately to me. It won't be shared.
* Before uploading, right-click the folder, click PROPERTIES. Look at the File Size to confirm that it's not too big for the free space on the server.
And, of course, save Project File AS routinely, giving it a unique # or name, so as not to overwrite prior saves. Using Save Project Files (no AS) will overwrite.