Install the current 64-bit release. 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.
Confirm that the PC video driver and Direct-X are up to date... https://www.nch.com.au/kb/10265.html
If this 'right-angle' split image shows up again, please take a screen grab and post a link to it here. Upload the file/s to a free server, such as Google Drive or MS OneDrive, get a shared (public) link, copy the link and paste it here or to me in a Private Message via the mail envelope in the top-right corner of this forum. If using Google Drive, if necessary change "restricted" to "anyone with link can view."
When reloading a project allow it to cache fully. The green line above most thumbnails should be complete. 
Under the preview window the blue line may eventually change color in some cases. 
For lengthy/complex projects this can take quite a while. Once cached, preview should be smooth.
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. From the HOME tab, that choice is available by clicking the chevron to the right of the Save Project button on the toolbar.