If an access violation error is being received when attempting to amend aspects of a leg when other legs of the same trip have been verified, you will want to start by reviewing the crew assignment.
Access violation example:
Within the trip view, look at the crew at the bottom right. Are there any assignments that are incomplete? Highlight the inaccuracy and choose "delete". Then review what the schedule shows after clearing the impacted assignment.
In this example, leg 1 was verified. However, after verification, leg 2 needs a PIC change. Highlight the original PIC assignment on the two legs and choose "verified legs". This will hold the assignment for the verified leg (#1) and unassign the individual on leg 2. Make any further changes needed, then "Save" to save changes and remain in the trip or "OK" to save and exit.