As others have already pointed out check the complete install, both sides, and make sure everything is secure. I would replace the wire and attachment hardware again as others suggested.
For what it is worth while not a hanging unit from the ceiling I did drop a DIY multi channel LED light in my tank. I had asked my daughter for help and she said yes, just needed a minute to finish something up. Well, me being me decided no need to wait and thought I had this. Up the ladder I go, reach up, start to move stuff around and out, wire bundle gets snagged, I tug, and then reach over and through the canopy only to miss and drop the connection clip. My eyes go wide, I say OH NO, and hear the splash while watching the unit gently float to the bottom of the tank. 30" tall. My daughter came into the room, said what the heck dad, why didn't you wait, and then moved me aside, reached in and got the unit out (at least it was unplugged before hand), and proceeded to rinse the unit in DI water. Her quick action saved the light and it still works amazingly well 2 years later.