I never cut anything off that isn't completely dead as there are always nutrients left in the p-bulbs that the new growth can use. Just remove the mushy/hollow roots and repot it into new medium. Then make sure that the medium dries out between watering but ensure that it doesn't stay completely dry for too long. I'd put it on a humidity tray to help the recovery. Make sure the water that stays in the humidity tray doesn't touch the bottom of the pot because the media will suck up the water and stay too wet.