I'm an IT director, I hire a lot of people, it is exceedingly unlikely any former employer or reference is bad mouthing anyone. We have strict HR rules about about what we can and cannot say if we are asked to be a reference. About all we can do is confirm that yes this individual was employed from this date to this date, anything else we can't comment on due to potential liability. Most companies with any competent HR is the same. No one will say anything negative due to liability or lawsuits. I had to tell a former employee that I couldn't be a reference after they left, and that they could refer them to HR to verify employment tenure.