Is it possible to stop the GPS from 'jumping' on a MT6592 phone?
Within 30 metres is sadly within the specification of GPS, so legally your phone works perfectly fine and does not qualify for warranty (refund or repair).

The issue seems to be common with your chip, and a software fix is known for rooted devices: http://www.chinasmartphonereview.com/gps-test-and-fix-for-mt6592-octa-core/. I don't know however if this is any different from the fix you tried, but it sure is worth a shot.


Ensure your device is rooted
Download Mobileuncle Mtk Tools
Launch the app and go to "Power GPS Search". Tap "GPS Set" and reboot.
Ensure you are connected to the internet and have all location settings enabled.
Launch the app again and go to "Engineer Model (MTK)" –> "Location Base Service". Tick GPS ON.