What computer operating system is involved in your Premiere Elements 10 and 13 experiences. Did you do all amount of significant work in 13 successfully before you updated to 13.1? There have been a few reports of 13.1 not working property after the update from 13.
Classically, you cannot open a project file from a later version in an earlier version. So, I am not understanding what you did related to
I created a project in v10, opened all the files as the v13 project
Nonetheless, I think that the first thing that we need to do is the assure the integrity of the Premiere Elements 13 instead.
1. Uninstall Premiere Elements 13/13.1 which you now have installed.
2. Do a free ccleaner run through (regular and registry cleaning parts) to get rid of leftovers from incomplete uninstalls/reinstalls)
If Mac CCleaner - Download
3. Reinstall with antivirus and firewall(s) disabled.
4. Work with the program as is at this point until you are convinced that the problems before the uninstall routine no longer exist.
Do not download and install 13.1 until you are convinced 13 works for your video projects.
I am assuming that you have gone through the typical drills
1. Does problem exist with or without antivirus and firewall(s) disabled?
2. Do you have the latest version of QuickTime installed on your computer with Premiere Elements?
3. Are you running the programs as administrator?
4. Do your Premiere Elements issues exist only with the use of DVD video files as source media? Have you ever seen these current issues when DVD video files were not involved? From what I am understanding, with these DVD video files, some were OK while others were not. Were the "were nots" from the same DVD disc?
Please review and consider.