Amp flashing on and off very fast on power up

I have an Audio Apex CAB45 that stopped working. When I try to power on with 12v it only flashes on and off very fast. However it will power on and stay on with low power at about 9v. No blown fets and no visible damage to any components. Does anyone have any idea where I should start looking? Any chance it could be a relay? I also do have another of these in working condition that I can use to test any difference if needed. Thanks for any help.
 

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