Sudden sneaking and bad compass health during auto

While testing my new Skywalker 1720 T tail with 3.2.3 firmware. I encounter a problem which I can not solve with my limited log analysis skill. I have completed a few test flight with it without any problem and decide to make a small change in motor thrust angle because it show slight nose down tendency while hand launch. In fact I have been using the same parameter for all the Skywalkers I build recently.

All seem fine until almost the end of third auto mission, it start to sneaking left and right. It become more severe after a few seconds and HUD report bad compass health. I decided to regain control and brought it down. To my surprise initially it always want to level out even though I still give it roll input but lucky this behaviour disappear a few seconds later and I brought it down safely.

I’ve check the compass interference it seems consistent all the way. GPS is good but NAV Bearing had sudden glitch while it start sneaking. What cause it to glitch ? I attach the tlog here hopefully I can get an answer to correct the problem. Should this happen in my real mapping mission work while sometime the drone is miles away, I may not able to see it again. Any help will be much appreciated. Thanks

My Set up
Skywalker 1720 T Tail. T motor 2820 830 KV, Multistar 4S 5200 Mah x 2. HK Pilot set ( 3DR do not ship to our country ), APC 12x8 prop.

tlog file is too large so I save it in Google drive … sp=sharing