pressure/temperature blowing

Hi All

I was doing NPT MD simulations and i observed that at some point temperature and pressure start blowing up and follow an upward curve (into thousands) with time, whereas there were another values fluctuating around expected means. There is a less probability that this is due to systemic issues. I have observed this kind of behavior earlier too. Can anyone explain please? I specifically wanted to know if this is any thermostat/barostat failure.

Thanks a lot!

regards
Chetan