ROS stereo camera calibration issues

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When viewing the checkboard recognition, I can see the points and lines lining up with the other camera. I have also tried with a different 8x6 and 5x8 board, but the results are still useless regardless. I have found that the problem is either with the stereoCalibrate function or the rectification used with the camera_calibrate. The distortion coefficient and matrixes are correct since I tested these myself.

Do you use undistorted images? If you use cheap cameras, the undistorted ROI can be quite small, and the checkerboard should be inside that undistorted ROI of both cameras. Sadly, I did not try camera calibration package myself, only directly in openCV, so I don't know whether ROS takes care of that

No, I do not use undistorted images. After the ROS camera calibration has finished, it gives you all the parameters together with a preview of what your new image will look like. I took only the camera matrix and distortion coefficients from it to test for myself if the undistortion is done correctly, which it is. The problem lays with the stereoCalibration and rectification.

So did you check the image itself after single camera calibration? Again, distortions outside ROI can be quite bad, so you need to take images for stereo calib inside the ROI. Just an example how bad it can be https://imgur.com/a/wngA10J