PSW 125 12" amp failures

Options
Hello,
I have 2 x Polk PSW125 subs. A few months ago one of them started making the heartbeat humming static noises that I've just found out is a pretty common issue. I just unplugged it and decided to use one sub for my setup.

Today my second one started doing the exact same thing.

Can someone please help me get this problem resolved?

I'm in Melbourne Australia.

Thank you very much! :)