try checking your ground

sand all paint away and make sure you have a good clean metal surface

Ground wire should be same size as power wire or thicker

Should use bolt to ground mot self tapping screws,

Ground is prolly the most important connection for your amp

Keep ground wire as short as possible the shorter the better

In cases like this i have found the ground to be the problem

use meter and check resistance between amp and ground wire/location, lmk what it reads