Process 101 Build Application Step 9 Not Working

can u share the interface code. 

Also if you open the community edition and open application W###AA Acme Automobile Reference Application, you can see the configuration for Process Model: W###AA PM Add Vehicle. If you run this process in debugging mode, you should hit the same error I did. Interestingly, the start form is not even opened and the process moves directly to the Write Record node.

bec we added interface in start node, interface not taking null values bec of required check. thats why getting error. if u take user input task or if u open directly in site page it wont get error. try it. 

bec we added interface in start node, interface not taking null values bec of required check. thats why getting error. if u take user input task or if u open directly in site page it wont get error. try it. 

Thanks for your response Pragna, but I am really confused, particularly as I have followed instructions as per the Appian Process Modelling 101  training. What I understand from your comments:

1. If you have a form in the start node of a process, this results in errors and not possible to run process flow in debug mode?
2. Is the Appian documentation and steps for the exercise incorrect? Do they need checking and revising?
3. The reference application in the Community edition also fails with the same error - has Appian not tested their own code?

I would like to believe it is something in my configuration but really struggling to diagnose to the root cause.

What do you mean by " if u take user input task" - please explain the steps as I am new to Appian?