Pumps are designed to pump liquids. When a pump is operated dry, all bets are off, and the pump will self-destruct prematurely through high vibration levels and resultant bearing and seal problems. Before you worry about anything else, I would strongly recommend that you ensure that the pump is always pumping a liquid. After that, you will then be in a position to isolate and identify any other challenges that might be occurring. Sometimes the “easy solution” will indeed work.