When a Area/Category associated with a high urgency value is updated, the update occurs automatically; however, when the urgency value associated with the Area/Category is low, the urgency value remains unchanged—and the same applies to the impact associated with the affected service.
This occurs when the Priority Matrix is enabled for incidents.
Service Desk Manager 17.4 and later
Component: Priority Calculation Matrix
This is by design and documented in the following techdoc link: Priority Calculation under "How Priority Calculation Manages Ticket Values"
The Priority calculation was designed to not override the customer's manually selected values and only escalate the tickets. De-escalation is intended to be performed manually, to ensure no unintended priority decrease. Changes to urgency, impact, or priority are part of the Priority calculation logic.