RTH wanky behavior

[neistow]

Problem

When using RTH, Cruise, and LOITER modes, the plane begins oscillating (?) on the yaw axis, then loses altitude and turns completely sideways.

I've attached a video with a sample footage (no black box, unfortunately). There might be a second or two of desync between the footage and the OSD, but overall, it represents an accurate OSD.

Things worth pointing out:

1. On all the footage, the home arrow seems to be alright, EXCEPT the last one, where it goes completely crazy (maybe OSD desync, but I doubt it)
2. I checked the GPS coords and compared them to the video footage, and they seem to be correct.
3. Plane is mechanically sound and flies well in ACRO/ANGLE
4. RTH seems to work fine till some point on the clip with autolaunch.
5. I did notice a weird behavior from my GPS: 2-3 timeouts and a couple of errors, also it alternated between 12 and 0 sats. This was when the plane was still on the ground, powered by a USB from a phone. There were no warnings/errors during the flight.
6. Don't mind the artificial horizon being way too down. I was messing with the osd_horizon_offset and left it set to -2.

Hardware details

Model: heewing t1 ranger
FC: Speedybee f405 WING (not mini)
GPS: HGLRC M100-5883 M10 GPS
RX: BetaFPV SuperD Diversity ELRS
VTX: Walksnail Moonlight

Software details

Firmware: INAV 8.0.1
Plane type: airplane without rudder
Enabled sensors: Gyro, Accel, Baro, GPS, Virtual Pitot

Additional info

Flight footage: https://youtu.be/D6zvXhlyaiY

Please let me know if you need additional info

[shota3527]

Hi, it is hard to debug via the DVR
Could you display the heading and the course over gound on osd next time you flying?

[neistow]

Hi, I will. Thanks for the reply

[MrD-RC]

I'm not being funny, but even in Angle it didn't seem very stable on the roll axis. What is the chance of recording a blackbox log and providing a diff all. What aircraft is this? A fair amount of the flights seemed pretty slow.

[neistow]

It is heewing t1 ranger. I can provide diff all, but I won't be able to fly in the next few months or so, but I'll record blackbox as soon as possible

[Allerhopp]

Is there any chance this behaviour is related to M10 GPS? My wing flew flawlessly with a Beitian BN180 GPS. I wanted to improve the waiting time for GPS fix (was about 4 min), that's why I switched to a BE182. Fix was indeed faster but the wing showed a very strange behaviour in position hold - very similar to the behaviour in this issue. The only difference between the two setups was the GPS type.
No time for a crosscheck, maybe next week ...

[sensei-hacker]

The M10 (BE) chip even with the small 182 antenna should be good enough in most cases. Unless you're in a canyon / between buildings or under tree cover, or there is a lot of interference from other RF sources.

The M9 (BK) is the higher performance chip, and a larger antenna improves performance. So a BK-880 would be "better".

The T1 isn't a tiny whoop, so you don't have to use the smallest GPS antenna.

But again, in most cases the GPS you have is sufficient.