There is a (besides the above mentioned ones) reference to this in the following publication:
Formation of N‑Nitrosamine Drug Substance Related Impurities in Medicines: A Regulatory Perspective on Risk Factors and Mitigation Strategies (https://pubs.acs.org/doi/pdf/10.1021/acs.oprd.3c00153) alias “introduction of a nitrosatable amine in the mix”.
However, besides the theoretically introduction, I haven´t seen this case in real-life confirmatory testing yet. But this may be a future topic of “excipient quality grade” where dependent on grade/source a certain amount of nitrosatable amine is introduced in the finished product formula.