does anyone have any troubleshooting recommendations thank you
Take it down and inspect it. I'd agree, likely water intrusion, corrosion, etc. Pay attention to the center coil and above, since damage there would directly impact the lower frequencies.
Take all the set screws out and make sure everything is clean and shiny, including the threads on the set screws. Clean the ends of the whips with steel wool, wire brush, etc. Inspect the coil, especially the base.
On the mount, do the same, pay close attention to where the coax connects. If this wasn't properly sealed, it's very likely water got inside the cable.
Look at the coaxial cable jacket, look for splits, damage, etc. Replace if necessary.
All antennas require some sort of maintenance. Purpose built base stations don't need much. These mobile and mobile/base conversions need a lot.
Low SWR on UHF doesn't necessarily mean that the UHF portion is working, it could just mean that the distance to the fault in the coax cable is at the right point in the cable to look like a suitable load.
