Deviation Management : Why you hve sent an Instrument for calibration? That was as a standrad calibartaion procedure or is it showing erraneous results or is it observed by QA-Compliance team or did this particular system is responsible for manufacturing deviation?
When such instruments come back what ever the reason might be, they should be a review team to review, look back into system and properly place such system back.
There should be a tracking team for such instruments where deviation cannot repeatedly occur.
You need toi develop a template why these has gone, what was verified, certificate of calibration etc etc.
After calibration some one from that external agency needs to wtach the system for its accuracy atleast during 2 cycles of processing.
As you mentioned such certificates must be reviewed and any flaws existing must be rectified by competent person in the organization
2.Vendor review and Quality agreements with vedors are very much essential. Quality agreements must contain who is attending to perform such calibration programmes and what is their training and certificate of training are much needed. If you look ICH Q9/Q10 agreements training is much needed and its mandatory. In this case since your company do not have this competency to perform --FDA looks in to such agency how copetrent they are and your review report.