I recently tried using Corel Pinnacle Studio, but the 'scrub' was not working. It turns out that, despite frequent Intel Driver Updates, my graphics driver was old. After a full GPU driver delete and install, the problem was resolved - and now I see improvements in Vegas too.
This made me think that this Vegas Forum could have a new top category of 'Hardware & Drivers', where specific GPUs and common computer systems can be listed with feedback on user experience and solutions.
PS - The Corel support asked for the following:
... I require a copy of your MSINFO32 report and a WinAudit report from your Windows OS.
To generate the MSINFO32 report, please do the following:
1. Press Windows Key + R. The Windows key is located between the Ctrl and Alt keys.
2. Type msinfo32 and click OK.
3. While viewing the System Summary node go to File then Save (Please do not use Export).
4. Save your MSINFO32 report as msinfo32.nfo on your desktop for easy access (you may delete the file once you have attached it to support case and submitted the case).
5. Send the file as an attachment on your reply.
And they used these reports to say that others reported issues with the Graphis Driver that I had installed, and gave instructions on un-installing the current then installing the latest:
I have gone through system reports and noticed that an old Intel Iris Xe graphics driver is installed, there have been reports from other users that old Intel Iris Xe graphics driver causes such playback issues, please install latest graphics driver from link below.
Also, see the link to uninstall graphics driver - https://www.intel.com/content/www/us/en/support/articles/000005598/graphics.html