We've finished a fairly major architecture change to work around this Vegas bug. We couldn't see Magix fixing it in a timely fashion.
The issue is caused by Vegas caching old files. When we replace the source media in the working folder for new customers, the file names are the same and Vegas incorrectly retrieves the previous customers file data, which is no longer valid. When TandemVids sets the length of the events to match the source media to be inserted, Vegas gives us the duration from a previous customer. It does this intermittently, which made it extremely hard to analyse.
Rather than building the project in the working folder, we now build the project directly in the customer's folder. This allows all source media files to have unique names due to the unique path for each customer's folder. As an added bonus, the customer's files are copied a single time. Previously the project was archived to the customer's folder after the build.
If you have any custom software, which relies on photos in the instance folder, it will no longer work. You'll need to add an additonal folder to the output using the Folders tab.
For DVD and blu-ray builds, the photos are copied to the folder configured on the Photos tab prior to the burn. They'll still be fine.
The changes are complete but they touch a lot of areas so testing will take several days.