The deficiencies observed by FDA inspectors are written down in the so-called Form 483. Unlike Warning Letters, those aren't available online and have to be requested individually by post. Yet, FDA's evaluation of findings listed according to their frequency is pretty unknown. This is a very easy way to find out frequently observed deficiencies. In the fields "Drugs" for example, the lack of or the non-compliance with written instructions is ranked first. The second position goes to failures in the investigation of deviations.
The observation summary counts more than 5.000 483 Forms - including in addition to drugs also further fields like foods which have been analysed separately.
Another interesting summary is the webpage with FAQs relating to the 483 Form.
The following graph shows an analysis of the 483 identified during fiscal year 2013.