With any request, schedule a follow up meeting to discuss the completed work, or to perform an autopsy if there was some impediment.

Make sure to actually say “autopsy”.

“Inquisition”, “colonoscopy” or “employment review” all work well too.

If you have two Bob’s definitely get them involved.

Then have a practice of letting such meetings be cancelled if the work is done and went well.

This can be done as a consistent and transparent inside joke. Humor often generates the social permission to communicate hard truths, by also providing psychological stress dispertion.

I cannot vouch for any of this, but please share your experiences.