Another thought, now I'm more awake, the tensioner could be seizing. This would show polishing/burning to the back face of the belt.
Tensioner could also be coming loose, so pushing at an angle.
Anything else driven, such as some water pumps, aircon, power steering, etc., can cause such issues.
If it is hydraulic power steering, with the pump driven from this belt, when the fluid is cold, first thing in the morning this time of year, applying full lock immediately or quickly can demand high fluid pressures which stresses the belts. (The first Rover 820, mid eighties, drove its steering pump from a camshaft, with a toothed belt. Many an engine destroyed on a cold morning as the owner reversed out of their drive, applied full lock, and stopped the inlet camshaft from turning!)