AC power drops out when GPU in use

Hi there. I've got an Alienware 15 R2 that has had multiple warranty calls in the past 6 months. Late last year I had to mail it in for repair as the AC adapter seems to stop working intermittently (for a few seconds) whenever the graphics card is in use for games. It flickers back and forth and slowly drains the battery and changes between battery and main power profiles.

I mailed in my laptop (was 2 weeks out of warranty period) and had it "repaired". Now the same issue has returned after only 3 weeks use. Support team believed it was just a faulty AC adapter, but I've tried it with an alternate one before I first sent it in. It doesn't seem to make any difference.

Has anyone seen something like this before? Any hope in fixing it? Or should I try and get a refund or replacement... This would be the 6th fault since I bought the device.