# [VOXL-SVC] WAIT_VIO: VIO velocity unstable (VIO backend converging) (30 s)

Source: https://forum.modalai.com/topic/5305/voxl-svc-wait_vio-vio-velocity-unstable-vio-backend-converging-30-s
Category: VOXL SDK and Software (https://forum.modalai.com/category/47/voxl-sdk-and-software)
Tags: voxl-sdk
Posted: 2026-07-02 15:50:33 UTC by RoyAzriel
Replies: 1 · Views: 1472

## RoyAzriel · 2026-07-02 15:50:33 UTC

Hi,

I was doing already autonomous mission again and again succefully with two drones.
later I also encountered few crashes some of them prety harsh. but I was able to recover. also sufered from px4-param being deleted/corrupted. 
Now I test everyting and I cannot get the first drones to work with my code. when I switch to offbaord it immidiatly lands:
VOXL-FC] heartbeat: armed=0 mode=OFFBOARD
[VOXL-SVC] authority revoked (pilot takeover / link loss) — standing down (no re-request).
[VOXL-SVC] WAIT_VIO: VIO velocity unstable (VIO backend converging) (65 s)
[VOXL-SVC] WAIT_VIO: VIO pose stale (70 s)
[VOXL-SVC] WAIT_VIO: VIO pose stale (75 s)

with a new drone out of the box it works great.
I suspect it has something to do with with overwritten params that I am not aware of. tried pulling the params from the good drone by px4-param show -a  and compare them. without a good conclusion. 
my second guess is that somehow the cameras or other elements are oscilating and make the vio speed estimation not good and that is why these two drone fail to start the mission.

can you help with a step by step procedure to eliminate the prorblem. I have tested the services, the cameras and it all looks fine.

BR,

Roy

## Reply by Alex Kushleyev (ModalAI staff) · 2026-07-06 19:51:57 UTC

Hello @royazriel , please take a look at our documentation, which has some testing tips : https://docs.modalai.com/voxl-open-vins-server/