Altitude suddenly becomes minus using realsense T265 navigation

Why does the altitude quadrotor on the mission planner suddenly change to minus? and when in landing mode, the quadrotor can’t land, instead it gets taller. I use realsense as non gps navigation. this crashes my quadrotor badly.

(Add: we couldn’t get the log)

Without the .bin log we can not help you.

And please do not use ArduCopter 4.0.x update to ArduCopter 4.3.6 ASAP.

I can’t download the log because I used guided mode (no arming from remote)
How can I get the log?

Guided mode also produced a .bin log file.

Could you help me to get the log?

what flight controller are you using. Lets try and get that log off to help.

I used pixahwk cube black and fimware ardupilot 4.3.0
I’ll send some logs with date 1980

there are some logs I have when I activated non GPS navigation

this is my logs

could you help me to find my log ?

which log do you think it is as that will help narrow it down? I see some have current time and date. Sorry I am traveling right now teaching

yeah. therefore, I am also confused because there is a log with the same date.
I think this is the log

You need to make sure you get GPS lock, before arming. That way the log date will be correct.

Not having a GPS fix will cause a 1980 date. in the logs

could you help me to analyze this log?