Why is my inverter evil?

so basicly heres what keeps happening i have a solar panel system and my inverter is set to turn on when the voltages is high enough and off when its to low by a large relay controlled by a controller but what keeps happening is the inverter will randomly start pulseing on for a second every 5 seconds for no reason it will be working fine then off..................on ..off......................on ...off.................. the relay is on and power input is fine it just does this then if i disconnect the dc for like 2 mins then try again it goes back to normal for a few hours what is wrong with this one? i also have anyone that does a similar thing but instead of that it just randomly gliches and drops to 50hz instead of 60 but again fixed by being dissconnected and reconnected..well temp fixed anyone have ideas?