Have you contacted Arc? They might fix it if you send it in. I had a Sundown amp with an RCA connector issue and sent it to them to be fixed. Didn't take very long and was cost was reasonable.
2013 Mineral Grey 335i | M-Sport, HUD, NAV, CF M Perf Trunk Spoiler, M Perf Grill, M Perf rockers, M Perf front lip