Hi Leo, I have the same problem . My antenna is stuck in the UP position on my 2002 Tribute V6. The nylon strip inside the antenna has probably worn smooth. It has teeth that are run by cog wheels inside the aerial body, so when turning the radio ON up goes the antenna, turning OFF the radio, down it goes.
I have just bought a Mazda Tribute/Ford Escape 2001..on replacement antenna on eBay from Online Auto Parts Australia
Hope this helps.