OEE lack and build back
Just ate 5 Oreos! Insane!
Assuming all people are equal (invalid, as trained operatives are required as operating instructions take so long to learn and are entirely likely to lead to error due to complexity and ambiguity) then the capacity constrained resource should be a machine. But it isn’t. Investigators are a different breed. Machine operators are a different breed. Investigators need to be line side and as part of the flow line. Don’t remove the need to osmosis and problem solve collaboratively though. Just facilitate it.
Stop thinking of him as a facilitator and instead confirm him in his role. If he wants to tick over to retirement then fine, but you don’t get to stop developing.