2002 Honda Accord all dash lights on and flickering

Hi,
I was helping a neighbor and noticed her car sounded funny. She popped the hood and I heard an awful grinding sound. At this point, she had no lights on the dash and no issues except noise. The noise was the alternator as the internal bearings were done. She bought a reman alternator at auto zone and I put it in. It was very easy. She fired it up and the sound was gone and all was good. The next day she found that while driving the dash lights would all light up and go out again. This includes the door indicator lights. I double checked everything and all cables and all bolts were tight. We thought the alternator was bad so she returned it and bought a new alternator (not a reman this time). I installed it and the next day the lights started flickering. I’ve heard of this before on Hondas but cannot seem to find a solution. I want to stress that I only removed the negative terminal from the battery, removed the 12v line from the alternator, removed the serpentine belt from the alternator via the tensioner and the mounting bolts. I put everything back as it was. Cables are tight. The lights do not come on at idle or when revving the engine in the driveway. Any thoughts? Thanks so much!