Regulations require that the critical process variables should be included in validation. This has been recently confirmed again by the FDA in a Warning Letter.
As almost always when it comes to process validation the FDA refers to 21 CFR 211.100 (a). During the inspection, the inspected company stated that it had difficulty determining manufacturing parameters for the manufacture of its drugs. This was reflected in the product records. Missing values for mixing speed and time were addressed directly. According to the FDA, there is no suitable control of the process to ensure constant product quality.
The FDA requires that the company perform an immediate risk assessment of patient risks associated with products whose manufacturing processes are not validated. The measures resulting from the risk assessment, such as retrospective chemical and microbiological analyses, customer information and recalls, should be clearly addressed.
You can find the exact wording in the FDA Warning Letter to Mariposa Labs.