I often get some very candid feedback, and have passed on couple roles because of what I've heard.
What sorts of signals do you look for in these answers?
Good: Addressing the problem, fixing the process.
Bad: Assigning blame, firing the responsible.
(The latter especially for a first instance, though if you've got repeat instances, I'd look first to management, then to staff, for cause.)
Another bad sign is if the cause for the stress is internal, and a pass sign is if it's either management or a major (or the only) client.
If you cannot find ways to eliminate internal causes of stress, or buffer those created by the commercial environment in which you exist, it's going to be somewhere on the continuum between toxic and fatal to me.
"Firing the responsible" may be an overly-strong comment -- putting pressure on the line rather than improving line management is the upshot of what I'm getting at.
Though truly boring can be a good sign if it's the result of good planning, drilling, practices, and rewarding competence. If it's from complacency, failure to recognise problems, or the ability to push fault or failure off on others (clients, customers, vendors, suppliers, other departments), not so much.
The good sign then is understanding why and how they got to boring.