Without being too simplistic, is it possible that this aircraft was past it's use by date? No matter what inspection or maintenance showed or was performed some other mechanical gremlin was about to surface.
This is what we call "limit of validity" (LOV) these days...
From FAA AC 120-104:
3. WHY DO YOU NEED AN LOV? If you properly maintain an airplane, theoretically you could operate it indefinitely. But structural maintenance tasks for an airplane are not constant with time. Tasks are typically added to the maintenance program as the airplane ages. It is reasonable to expect, then, that the current structural maintenance tasks may not, at some future point, be sufficient for continued operation. Maintenance tasks for a particular airplane can only be determined based on what is known about that airplane model at any given time—from analyses, tests, service experience, and teardown inspections.
Same philosophy applies to systems, although it is much easier to completely replace all parts, as long as spares are still available...