Though I cannot answer your question about sourcing/ordering a motor replacement, I just want to point out that there are two washers placed in between each motor and arm on the drone frame. Each arm has the washers installed in a specific location to aid handling. Observe and take note of the washer position so when you take off and replace the motor, you will be able to properly reinstall the washers

You can also get a different idea of what the camera is seeing by adding a "-t" to the end of the code line. For example: "voxl-calibrate-camera stereo -t "
This makes it easier to gauge if the lighting is good and can provide a different perspective which might make calibration easier.

@Syed-Omair Follow the Red/Black/Yellow cables coming out of the flight core to the receiver

Easiest way to get to the ESC would be remove the connectors that are circled in red

Remove the circled screws [PH1 drive] and cut the zip tie with the arrow pointing towards it

Remove these 2 screws [PH1 drive]

Remove these 2 screws [PH1 drive]

And finally, to get the board stack removed, you'll unscrew these 4 hex screws [1.5mm Hex Drive]

WHEN REMOVING THOSE HEX SCREWS, BE SURE THE CIRCLED STANDOFFS DO NOT ROTATE AT ALL, THIS COULD CAUSE THE SCREWS COMING FROM THE OTHER SIDE OF THE STANDOFF TO GET LOOSE
Keep these by rotating by carefully holding them in place with needle nose pliers or something similar

When re-assembling, just make sure all screws going into those standoffs are nice and snug (coming from both the top side and bottom side)

@griffin Take a look at the drone and realize each motor has 3 wires and 3 pads on the ESC board they get soldered to. Each motor must be soldered to it's corresponding set of 3 pads. Once you get the wires long enough to be mounted to the frame and solder up to the pads, make sure you match your new motor wires to the correct set of pads for that motor (reference which pads your motors are currently soldered to). However, you won't have to worry too much about which wire goes to what pad (within the 3 pads available for your motor). If a motor is spinning the wrong way, you can reverse the motor rotation within QGC in the "actuator" menu. Alternatively, you can swap 2 of the wires with each other within the 3 pads/wires that are meant for that particular motor.
https://drones.stackexchange.com/questions/80/how-can-i-reverse-the-direction-of-a-brushless-motor
This link describes the same process, just in different words

@Syed-Omair Follow the Red/Black/Yellow cables coming out of the flight core to the receiver

@bendraper Are you working with a VOXL 2 flight deck?
What kind of values are you getting for the right and left intrinsics?
Have you tried running the whole calibration a few times from a position where the left and right intrinsics are good? Sometimes it's as simple as a lighting issue and a small adjustment in the positioning of the device relative to the room's lighting can make a meaningful difference. And sometimes running just extrinsics will not produce an acceptable result even if your intrinsics are good.

If you've already ran through several calibrations with no success, I wonder if there is any offset in the cameras' positioning. This can come from a physical offset in the stereo camera mounting, but it can sometimes be related to the internal construction of the sensor itself (sometimes the image sensor is offset to the lens which leads to the stereo images not being on the same plane).
If you send a screenshot of the camera calibration overlay screen with your calibration board's top edge aligned with the top edge of the camera's view, it would provide me some more insight into your particular setup. I'm specifically looking to see if, for example, on one side you might have the top of the board aligned with the top of the camera's view while the other camera's image may have the top edge of the board significantly over or under the top of the camera's view.

@rohitpillai do you have a spare mcbl-0001 you can try on this setup?

@rohitpillai When you removed the extension cable, were you still plugging the tracking camera into the M0054 board directly?

@Tamas-Pal-0 What is the "quality" readout before takeoff when you run voxl-inspect-qvio ?

@張為超
run "voxl-inspect-qvio -n" to see a readout of qvio positioning and number/quality of features the camera is seeing

I would recommend re-calibrating the compass within QGC to possibly fix the issue with altitude mode issues

I would also recommend cleaning the camera lenses with a clean cotton swab or microfiber cloth as the camera might have gotten dirty, resulting in interference with qvio's ability to work

QVIO is used for height/positioning when you are running your drone on the indoor vio parameters. This can be set up on both M500 and Seeker drones

Though I cannot answer your question about sourcing/ordering a motor replacement, I just want to point out that there are two washers placed in between each motor and arm on the drone frame. Each arm has the washers installed in a specific location to aid handling. Observe and take note of the washer position so when you take off and replace the motor, you will be able to properly reinstall the washers

@Daniel-Ryu The stereo sensors' lens can be adjusted which will change their focus. Looking at the videos you provided it seems to me that you should be able to achieve a lower reprojection error if you adjust the focus on the units. It looks like the VOXL1 is getting a better reprojection error number because the cameras are fairly close to in focus and there isn't much blurr/fuzz in the video stream. On your VOXL2 setup it looks to me that either the camera is out of focus or the lens is dirty.

To adjust the focus on our stereo cameras twist the lens housing clockwise or counterclockwise similarly to how you would on a DSLR lens. Look closely at the stereo cams and you will see 4 flat edges. I recommend using a 6mm wrench to engage 2 of the flat edges; from there you'll be able to rotate and adjust the lens as needed. It is possible to use something like tweezers or small pliers to accomplish this however I recommend against that method because it is too easy for the tool to slip off and end up scratching the lens.

To clean the lens I recommend using a clean microfiber cloth, a lens tissue, or a fresh q-tip