VueScan 9.8.45. February 23, 2025.
Ok, but check the version number anyway.
I see you've posted in another site and a member said he changed his computer, then everything was fine. How old is your computer, and is it a Mac or Windows PC?
If it's a Mac and you like Macs, changing to the new iMac M1 may be more suited for a new Plustek scanner. I know nothing about the latest Windows PCs, I gave Windows away many years ago. It's macs4Me now lol, they are stable, secure, and the iMac M1 has a solid state HD, the computer stays cool, even on a hot day, as it is here now. I can't give any advise on Windows PCs, they are a distant memory.
You say that your bundled Silverfast does an excellent job for 35mm and 120, but it's limited in what it can do with your Plustek, is that right? Bundled Silverfast is a bare bones Silverfast, they want you to buy their bells and whistles version, if you can afford it.
Getting back to the guy on the other site who sorted the sorted the problem by changing his computer, did you DM him or find out somehow which computer he changed to? Sounds like he had the answer.