4710MQ throttling issue

I have had a P150SM-A since October, to start with I was confused why my 4710 only ever turbo'd up to 3.2, did some googling, changed the multipliers in XTU so all were x35 and I undervolted by ~80mv and all has been well! Until a few days ago I noticed when playing arma 3 which is very cpu intensive, that my processor all of a sudden cut itself back to 1.5Ghz with no explanation and wouldn't come back up without a restart? It did this a few times and then my whole laptop just cut out, no BSOD no errors it just turned straight off. Then it did this again the other day but wouldn't come back on for like 24 hours? I'm a little bit worried and also quite tempted to RMA this, just wondering if there is something I can do to work out if there is something wrong with the processor or the power management in my mobo?
The bizarre thing is that the stress test on XTU manages to hold 3.49Ghz constantly, yet when playing games it seems to cut back regularly as if there isn't enough power?
I have the 180W adapter and a 980m so i'm considering upgrading the power adapter?

 

Is your battery being used when it does this? It may be that your brick is not quite right.

 

Not that I have noticed, that is if you mean is it being discharged while I'm gaming with the adapted plugged in.
I was thinking that maybe if it has been running at near its max output while my laptop is at load it might have degraded a little and not be putting out as much power/consistent power?