isCallable fails

[tsbockman]

On Friday, 22 January 2021 at 00:59:32 UTC, tsbockman wrote:
> 2) Remove, simplify, or mock up/stub out (like for unit tests) 
> some large chunk of the remaining code in the program, from a 
> part of the program that I *think* is unrelated to the error.
> 3) Re-test the program.
>     a) If the failure goes away, goto (2) and try again by 
> removing a different part of the program.

I should clarify here that when I say "try again" I mean from a 
backup of the last version of the reduction-in-progress that 
*did* demonstrate the failure.