He has one of those Shocktech Banjo's supplied with the body. Look in his sig, ST body. Those body kits came with a modified banjo fitting.
ST Ion Body Kit
Read the third paragraph:
The bodies also include the proper banjo fitting
to ease assembly and disassembly. Kit also includes pre-fitted hose, hose barb and extra o-rings.
Sounds like you need to contact Shocktech and buy a new banjo fitting.