The Patient Reminder Queue Job generates a system message on completion indicating: the number of reminders queued, cancelled and skipped.
The skipped reminders includes both reminders that can't be processed:
due to error
as there is no Reminder Type - Reminder Count corresponding to that of the reminder
The latter case isn't necessarily an error; it simply means there is no further processing to be done on the reminder until it is either completed or cancelled.
The Patient Reminder Queue Job should exclude these reminders from being reported as errors.