...And is that on all bands as well?
If you have not already tried it, just try doing a factory reset before looking for hardware causes for the problem - it could save you from disturbing the hardware / dismantling things unnecessarily.
If, after that, it looks like a hardware problem, the service manual (technical supplement) should be a good place to start.
http://www.fracassi.net/iw2ntf/manuali/FT817_serv.pdf