What is your Shotcut version?
Can you upload the full
application log and the export log?
When it fails, does it always fail at the same spot? Or does it fail at a random percent?
From your test results it is difficult to conclude if the transition is causing the failure or if the failure is just intermittent. You could also try removing the transition and creating a new one.
The exit code failures are infrequent, inconsistent, and do not happy to most people. We have been working to reduce them, but if a failure does not happen for a developer, then the developer can not fix it.
We have a collection of advice here which may be helpful:
I am a developer and I do not know what that is. The front end GUI is written using QT and the backend processing (that is used for export) is mostly written in C, but some filters do use the QT library.
No. There is an EDL export feature in the File menu, if that is useful for you.