My understanding is that FDA actions in regard to MDR noncompliance depend on the nature of the noncompliance...i.e. if reports were not submitted in proper form for minor reportable events, and if the FDA accepts that an error or a faulty system was responsible, that's important but not critical.
If on the other hand a report was not properly submitted for a patient death or serious injury, especially if the FDA thinks that the device may be causative, the risk of a repeated event may be significant and the report may have been intentionally not submitted, the FDA is likely to regard the matter as critical and to respond accordingly.