Black Current Frame and stuck Map Viewer despite correct topic subscription (D435i Monocular)

[zzy7569]

Environment: Ubuntu 20.04, ROS Noetic, RealSense D435i.
Problem: Current Frame is black and Map Viewer is stuck while running rosrun ORB_SLAM3 Mono.

Connection Verified: rqt_graph confirms that the /ORB_SLAM3 node is correctly subscribed to /camera/color/image_raw.

Symptoms: The Current Frame window remains completely black; the Map Viewer shows no activity.

Error: No tracking logs appear after Starting the Viewer. A Bus error (core dumped) occurs on exit.

Log Output:
rail@rail:~/ORB_SLAM3$ rosrun ORB_SLAM3 Mono Vocabulary/ORBvoc.txt Examples_old/Monocular/RealSense_D435i.yaml /camera/image_raw:=/camera/color/image_raw

ORB-SLAM3 Copyright (C) 2017-2020 Carlos Campos, Richard Elvira, Juan J. Gómez, José M.M. Montiel and Juan D. Tardós, University of Zaragoza.
ORB-SLAM2 Copyright (C) 2014-2016 Raúl Mur-Artal, José M.M. Montiel and Juan D. Tardós, University of Zaragoza.
This program comes with ABSOLUTELY NO WARRANTY;
This is free software, and you are welcome to redistribute it
under certain conditions. See LICENSE.txt.

Input sensor was set to: Monocular

Loading ORB Vocabulary. This could take a while...
Vocabulary loaded!

Initialization of Atlas from scratch
Creation of new map with id: 0
Creation of new map with last KF id: 0
Seq. Name:

Camera Parameters:

• Camera: Pinhole
• Image scale: 1
• fx: 382.613
• fy: 382.613
• cx: 320.183
• cy: 236.455
• k1: 0
• k2: 0
• p1: 0
• p2: 0
• fps: 30
• color order: RGB (ignored if grayscale)

ORB Extractor Parameters:

• Number of Features: 1250
• Scale Levels: 8
• Scale Factor: 1.2
• Initial Fast Threshold: 20
• Minimum Fast Threshold: 7
  There are 1 cameras in the atlas
  Camera 0 is pinhole
  Starting the Viewer
  ^CShutdown

Saving keyframe trajectory to KeyFrameTrajectory.txt ...
Bus error (core dumped)