troubleshooting advice

[Jhunt94]

I could post this in the manufacturer thread, but it's not my amp and not my choice what to do so I figured I would post this in here. A little background, my uncle has a boat that has 4 6.5s speakers on it. Originally it had a memphis audio amplifier supplying power to the speakers, but it went out on him so I recommended and amp to him and he bought it. I installed the amplifier on the boat, double checking connections, making sure everything was right, tuned it with DD-1 and CC-1, and it was working great. Then that weekend we were out on the lake, listening to some tunes, and then the sound cut out. I checked to make sure that the amp wasn't in protect and was powered on and everything was fine, it just acted like it wasn't getting signal so I wondered if maybe the rca's on hu had broken. I've seen in some cases where people will put head units in a boat and then after years of being on the boat and being shaken around, the solder joints break so I figured that's what happened here. I went back out to the lake yesterday to do some troubleshooting, and first I took and aux cord, ran it through a splitter into the rca's to see if the amp was still putting out and it was. It was working perfectly, so again I figured it was the hu. Then I hooked the hu back up to the amp, plugged my phone into the aux port, and the amp was back working with the hu, but it didn't seem like it was as loud as it once was. I figured out that I didn't have my phone volume all the way up so when I turned it up the signal cut out again. After that, no matter what I did, whether I plugged my phone straight into the amp or through the hu, I couldn't get anything out of the amp. Also I checked the signal coming from the hu with my DD-1 and had signal.

So my theory and question..Are the rca inputs on the amp bad? or am I missing something?