Product defect, there are two logic flaws around this functionality.
This has been reported to Symantec Engineering and will be fixed in a future version of ServiceDesk.
These problems are in the open Problem Feeder project and can be fixed by making a couple modifications:
Open the SD.Feeder.ProblemCreation project.
Go to: 'Set New Problem Data [4.82]' Embedded Decision Model component > 'Set Priority According to Impact/Urgency Matrix ' Embedded Model component
Edit the 'Set Ticket Priority to Matrix Value ' Single Value Mapping component > Mapping Definition '...' and change the ProblemTicket.ProblemPriority (right side) mapping to VarFoundMapping[First].Value (from current VarImpactUrgencyMatrix[First].Value).