01 QX4 Blown Fuse and buzzing noise from Driver's side Ballast? Does it even when I switch ballasts

[Legend11]

My driver's side headlight went out a few weeks ago and I assumed it was the ballast issue (swapped in a known working bulb, swapped relays). I ordered a new one and had the same problem of it not turning on. I was confident I received a bad part but discovered there were 2 20 amp fuses in a fuse box on the passenger side. To my surprise, the driver side 20 amp fuse was blown. I replaced the fuse and tested with the new (ebay tested used) ballast and the light came on without issues. I noticed a strange buzzing found and assumed the part I received was having the issue. Just for the heck of it, I swapped in the original ballast to test and the headlight came on, but with the same buzzing noise.

Now I have 2 questions:
1) What is causing the buzzing sound with both ballasts on the driver's side headlight
2) What caused the driver side fuse to blow in the first place.

There has been a lingering issue with the truck since I bought it. Occasionally, the driver's side headlight will flicker. It would not do it all time the time, but I assumed it was a sign of the ballast going bad. Now with the buzzing noise, I'm not so sure. Anywhere I can check?

By the way, my dad's truck (also an 01 QX4) has gone through 2-3 ballasts since he bought it 4 years ago. My experience has been that this part can have issues and probably why I assumed that's what it was. It appears my truck is having a different issue.

Thank you,