If you believe the issue is with your internal auditors, then as suggested I would seek additional training for your staff, shadowing an outside consultant would be a good way of accomplishing this while also getting an outside perspective on your systems/processes.
It sounds to me, however, that from Top Management's perspective, the problem is located in your internal audit process. Do they have specific quality goals defined, what quality performance improvements are they looking for, how is this measured...look at your improvement metrics and identify the history...
has your company shown improvement in these areas if not, why?
It sounds like your executive management wants more focus on the big picture. Supply them with overall performance metrics, analysis, history, and work with them to define what goals they want to meet...once this is accomplished you can better direct your auditors and augment your internal audit program accordingly.
Best of luck to you and your staff.
