[Python] OpenCV cannot read yaml

I am trying to run ORB‑SLAM3 inside a Docker container on Ubuntu 20.04 with CUDA 11.8 and OpenCV 4.5.5.

I have mounted my yaml file as read-only. Inside the container file exists.

Why I try to launch the monocular example I get:

terminate called after throwing an instance of 'cv::Exception'
what(): OpenCV(4.5.5) /tmp/opencv/modules/core/src/persistence.cpp:671:
error: (-215:Assertion failed) buf in function 'open'
Aborted (core dumped)


I have tried:

• Using existed example from SLAM developers - same error.
• Figuring out if OpenCV exist inside the container - it is!(OpenCV 4.5.5)
• Ensuring proper yaml formatting.

%YAML:1.0
Camera.type: "PinHole"
Camera1.fx: 1400.0
Camera1.fy: 1400.0
Camera1.cx: 950.0
Camera1.cy: 540.0
Camera1.k1: -0.02
Camera1.k2: -0.00115
Camera1.p1: 0.0
Camera1.p2: 0.0
Camera.width: 1920
Camera.height: 1080
Camera.fps: 30
Camera.RGB: 1

ORBextractor.nFeatures: 2000
ORBextractor.scaleFactor: 1.2
ORBextractor.nLevels: 8
ORBextractor.iniThFAST: 20
ORBextractor.minThFAST: 7

Viewer: 1
Viewer.KeyFrameSize: 0.05
Viewer.KeyFrameLineWidth: 1.0
Viewer.GraphLineWidth: 0.9
Viewer.PointSize: 2.0
Viewer.CameraSize: 0.08
Viewer.CameraLineWidth: 3.0
Viewer.ViewpointX: 0.0
Viewer.ViewpointY: -0.7
Viewer.ViewpointZ: -1.8
Viewer.ViewpointF: 500.0

udp:
ip: 127.0.0.1
port: 5557
extra_fields: [22.5, 39.0, 0]
verbose: 1


So I have few questions:

What does buf in function 'open' mean in OpenCV YAML parsing?

1. How can I verify that OpenCV can correctly read my YAML inside a container?
2. Could this be related to the Docker filesystem (read-only mount) or OpenCV build?

Any help on debugging OpenCV YAML loading in Docker with ORB‑SLAM3 would be greatly appreciated.

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