Should I Fix Attic Airflow Before Adding More Insulation?

I’m planning an attic insulation top-up, but I want to inspect the ventilation path first rather than burying a moisture problem under more fiberglass.

The house and roof are both about 20 years old. The attic currently has roughly 6 inches of loose-fill fiberglass, with some thinner areas near the eaves. I can see soffit vents from outside, but I’m not sure whether the original rafter baffles are continuous or blocked by insulation. There’s a ridge vent, although I haven’t confirmed that it’s open along the full ridge.

There hasn’t been obvious dripping, but I’ve noticed a little winter condensation on a few roofing nails and some frost after very cold nights. The insulation also looks uneven near the eaves. Before adding more, I’m considering checking for:

- Clear soffit-to-ridge channels in every rafter bay
- Compressed or missing baffles
- Bathroom fan ducts terminating properly outdoors
- Air leaks around ceiling penetrations, wiring, and plumbing
- Mold or damp insulation that should be investigated rather than covered

Which of these checks are reasonable for a careful DIY inspection, and what findings would make you stop and bring in a roofer, insulation contractor, or energy auditor before adding insulation?