Can you please elaborate the physical location where switch installed? In such cases power fluctuation is one of the main issue. Is any inductive load commissioned on this main line or are your catx cables running near to such load? This may also results a failure of switch ports .
<b>Try to eliminate all possible suspected objects and then try.</b> If possible install small rated UPS to power up the switch.
3 years back I faced similar situation. The A/C adaptor for the switch burnt third time which in turn burnt the 230 Volts line along with the switch and the interior of the reception of business hotel although it is installed in the rack with controlled power. But in my case, it was predictable failure of power adapter.