I have the same problem. With m'y ep 600 amp v.2 and i am enjoy with Axiom after warrantie service.
Brent accepting replace my v2 amp for brand new v.3 amp.
It is normal with électronics having some probs And i am consider i am on l'y ont Lucky...

And if you sent back the sub probably résolve yourte problems

Robert Lussier