Slow/Choppy After Upgrading

I have been using the free version of PDF Architect for years and finally decided to upgrade to the paid version. It always worked great, until now.

Even the simplest PDFs cause serious slow down. Scrolling is choppy, mouse movement is choppy when the cursor is over the PDF.

Even when a pdf is not open, the cursor moves slowly when hovering over the thumbnails.

I have a very fast machine - a new Dell XPS 17 (2020).

What is the solution? Thank you.