Word(s) to describe persons that leave a company and have a lot of information in their heads that is lost [duplicate]

What would you call the situation/a person with a lot of knowledge about a company that leaves the company, and the information is no longer available because the person left?

I'd like to use the word(s) I'm looking for in a sales pitch like this: "Stop being affected by <situation/persons>!"

E.g. a senior engineer who's been with the company since the early days and knows a lot of things that are not documented and all the other engineers rely on them for context?

"Stop being affected by the loss of institutional knowledge!"

The term is a littler broader, but includes knowledge held by employees and former employees:

institutional knowledge (n.)

Institutional knowledge is the combination of experiences, processes, data, expertise, values, and information possessed by company employees. It can span decades and comprise crucial trends, projects, perspectives and that define a company’s history.

Institutional knowledge takes many forms. Some of it is intentionally developed while other information is learned on the job and possibly even intuitive. The International Federation of Library Associations and Institutions offers the following categories for institutional knowledge:

Explicit/tangible: documents, records, reports, etc. that can be viewed, stored, and transferred

Implicit/intangible: personal anecdotes and context, skills, and intuition that can be transferred person to person through mentorship or training

Both forms of institutional knowledge provide value, so the most successful companies find a way to manage both. eduflow

"Institutional Knowledge: When employees leave, what do we lose?"

When employees leave a job, of their own volition or not, employers lose the institutional knowledge or history that they take with them, and many organizations lack sufficient transfer programs to stem the loss.

Andrew M. Peña; at higherEdJobs (2013)

The phrase "firm-specific knowledge" could be useful here. For example, "We are struggling to replace workers with a high level of firm-specific knowledge."

"Firm-specific knowledge" conveys the idea that the knowledge lost is specific to a particular institution (in this case, the company) rather than more general knowledge.

Whilst the term may seem a bit clunky for everday conversation, it is used extensively in the academic literature on economic theories of the firm.