If you want to find the reason of a bug, you need to read the application log file:
– runtime/logs/app.log
If your app.log file is very big, I suggest following these steps to find the error message easily.
1. Copy the app.log file to a different location (Backup)
2. Delete the app.log file
3. Try to replicate the error (Eg. Submit your form)
4. Open the app.log file (it’s auto generated) to see the kind of error message and where to fix it.