Hi

You might try an epoxy like Gorilla Glue (click the link below). I’ve had my Sub G2 since the upgrade from Sub G1 with no issues of the rubber feet falling off. Typically once the sub is in place it’s never moved. Are you moving/sliding the sub across your flooring? If so yo may experience the same issue again. 

https://www.gorillatough.com/product/original-gorilla-glue/?gclid=EAIaIQobChMI9pu6uofO_wIV_yKzAB3EFAPvEAAYASAAEgJ-K_D_BwE

I never dragged it. I move it once a year when the carpet is steam cleaned. 

I don’t think there was any accusation there, just speculation that it might occur again. Sometimes, there just isn’t enough glue to ensure total adhesion. I think what @AjTrek1 was suggesting was being aware, in case the machine that was gluing them on might be running out of glue, or there was some random extra dust, or whatever, and it may happen with other feet.