Cracked traces can be extremely difficult to locate, especially if they are under the resist coating. Bright light from behind the board can help.
Only had this a couple times but I won't forget the struggle.
I had a driver fail in that manner one time. Had them outside for a party and in got very humid as the evening went on. softened the paper and the voice coil parted from the cone. Not nearly as dramatic as that, was able to sim and reglue.