There is sometimes a metal spreader bar that is located between the spreaders to keep them from compressing the mast, and synthetic lines can cut that in half. If that happened I'd expect it to fall free, not clang around. Similarly, something could break free from the mast truck and lodge partway down.
But metal on metal clanging, that's a good trick. In any case it means time to pull the stick, and once you've gone to the trouble of doing that, inspect and refit
anything that's not right in it.
Metal conduit would be unusual but a PO could have done anything. Usually it would be secured to the aft side of the mast (perhaps hidden by an external sail track?). Once you have the mast down it should be obvious what/where is attached, and if it is pop riveted to the rear of the mast, you just need to drill out the rivets. Use a drill bit stop or depth
guide so you just drill the rivets, without plunging into the wires inside. Of course, a PO could have simply GLUED in some conduit, and the glue failed.
A good time to check the wires and the antenna
coax, since they can rot
out quietly. Many folks would say REPLACE the coax while the mast is down, since coax degrades over time and the wieght of it hanging, vertically, will deform it and degrade the performance as the conductor and jacket stretch at different rates. (It needs to be strain relieved, tied off every foot or so, to really prevent that. Not always possible.)