Looks like Challenge 7 is not working for me.. I tried with 2 separated Playgrounds from the scratch and it still fails with weird error, even though I think I've done everything right. I have no idea what else I should try.

Error message:
There was an unhandled exception. Please reference ID: GFXKWRGA. Error: Faraday::ClientError. Message: BAD_REQUEST: Specify a valid value for the source parameter.

I'm getting this error: Challenge Not yet complete... here's what's wrong: 
Opportunities with the stage of 'Awaiting Approval' and a Discount > 0, did not kick off an approval process named 'Approval for Package Deal'.

Here is what I submitted:

Object: Opporunity 
Start Process when created or edit

Criteria 
Conditions are met
[Opportunity].StageName Is Changed True
[Opportunity].StageName= Awaiting Approval
[Opportunity].Discount > 0
All conditions are met (And)

Immediate Actions
Object Opportunity
Approval Proccess: Specific Approval Process- Approval for Package Deal 
Submitter: User field from a record- [Opportunity].Owner.Id

Update Record
Record: [Opportunity]
Criteria: updated records meet all conditions
Filter: Discount Is null= true
New field: Stage=Scheduled

Criteria
Deposit Made
[Opportunity].StageName = Deposit Made

Immediate Action
Update Record
Record: [Opportunity].Fulfillments__r
No criteria
Status= paid deposit

Criteria
Cancelled
[Opportunity].StageName =Cancelled

Immediate Actions
Update Records
[Opportunity].Fulfillments__r
Status= Cancelled

Thank you in advanced!