Drew Adams <drew.adams@oracle.com> writes:

>> I guess this is either a bug in cus-edit+ (wrongly assuming any of
>> customized-value, saved-value, standard-value can be `eval'ed in any
>> buffer), or it's a bug in Auctex (for putting a customized-value,
>> saved-value, or standard-value that can't be `eval'ed in any
>> buffer).
>
> The cus-edit+.el code for this is essentially the same as the
> cus-edit.el code for commands such as `customize-rogue'.  And
> such commands are intended (of course) to be usable with any
> buffer current.

Indeed, the OP was able to reproduce the error with the normal customize
interface (see above), so the problem isn't with cus-edit+.

AFAICT, the problem is that auctex uses a standard-value for
Tex-auto-global that includes (file-name-directory load-file-name) as
part of the expression.