The imbalance sensor system has nothing to do with the suspension, and in 35 yrs working on Bosch i have never had to replace the suspension on any machine. The imbalance sensor system is in the pcb it measures the voltage generated by the tacho coil on the motor. When you have an uneven load the drum goes down one side faster than it goes up the other and the voltage is erratic triggering the system. If your machine used to spin a single bath mat once ,you were lucky, it usually never spins a single heavy item, and is designed not to, to prevent damage. this is not a fault. Cheers
Kenjo
November 2013