Rockford bd1500.1 going to protect mode

hi guys, recently buy a rockford bd1500.1 amp, right now it is connected into 4 ohms, supposedly it can go down to 2 ohms, and while playing in 4 ohms, when volume is 3/4 of the total and when bass hit, amp goes to protect mode. I switch the radio off and inmediatly on and amp starts playing again. Amp is not hot, and it sounds cristal clear. No evidence of malfuncition inside amp. Any thoughts??