@HopelessDemigod Hmm. Not much to fail with a dipole. Haha.

I'll place my bets on:

Moisture / water in the balun.
Water in the coax.
Near lightning strike cracked the ferrite in the balun.
Cold solder joint / corrosion.
Parted wire. (It's happened to me one time that insulated solid wire parted and was held together by the insulation. So perfectly fine looking wire, just not conductive from one end to the other. Hahaha.)

Good luck. I'm curious what it is.