I had this issue with an AX760i and I just asked them to replace it with newer HX850i. Technically lower end, but it does the job and doesn't have any such issues as far as I can tell. It also has a newer fancier custom FDB fan, instead of the disappointing Yate Loon fan they stuck on the AXi series, so it should be quieter anyway. RMA is still processing, so I wont know for a while yet!
Also @jonnyguru, you responded to my thread and said the AXi series never had this problem, but now you say it does? What changed man :P
Edit: The AX1500i is does not have this issue, it's a newer unit and has a version of the new FDB fan.