Listen, I get your frustration, guess who had the same thing happen to them. Truth is, Thrustmaster T300 (TX) is great wheel, outstanding in its price range, and also very flawed product, plagued with quality issues. It is both those thing at the same time.
I am about 90% sure of what is wrong with your wheel and what you can do. I'm gonna mark, 1) what is the fault of your wheel, 2) what you can do next. Based on personal experience with my T300.
0) Side-note. In video you provided the wheel base is opened, hence no manufacturer guarantee, but you can always try playing dumb, or claim that you bought it like that. Right to repair is very important, not that long ago manufacturers provided manuals, schematics to end user so they can fix their product. Now days, if you peel a sticker, or there are marks on screws from screwdriver, even when nothing is damaged from opening the device, and device is clearly malfunctioning in a way that could not be caused by simply opening it, they will deny guarantee and not even give you info for fixing it. You gave Thrustmaster money, in return you must receive a functioning product, that is of coarse if your wheel is still covered by guarantee. Just because companies use technicalities to screw over their clients does not mean their are right.
1) What is the fault of your wheelbase. I am simplifying a lot. In T300 there are 2 magnets, one is the motor's magnet (aka motor itself), the other is a small one put at the other end of the motor's shaft for the hall-effect sensor (counts rotation, knows rotation degrees). Since they are on the same shaft (axis), they are rotating 1:1 (aka if sensing magnet spins 12.4 time, then motor's magnet spins 12.4 time). But, for the wheelbase to function, the wheelbase must also know motor's magnet pole position at all times. Both magnets are on the same shaft and both are supposed to be fix to the shaft, then if Thrustmaster calibrate the motor (aka tell wheelbase motor's magnet pole position), and the other magnet (hall-effect) counts rotations, you always know where motor is, and how to turn it clockwise or counterclockwise. Well the glue the holds the motor's magnet to the shaft fails on T300 (TX) (common problem), and the magnet can rotate relative to the shaft. What that means is, motors magnet's pole position changes but old calibration stays. In one rotating direction coils (stator) are "rushing" the magnet (rotor), and as a consequence "lagging" in opposite direction. That is why your wheelbase turns very fast in one direction and slow in the other, guess who experienced the same thing. If glue fails completely, then there is no more force feedback. If glue fails where the magnet slips a little bit, then this happens (mine wiggled 5-10°, because of big "factory" glue smear it could not rotate more and fail completely)
In short...
Glue that holds motor's magnet to its shaft has failed, causing factory calibration to be not correct for the new magnet's pole position.
Or... your motor has partially unglued itself, no more spin right.
2) What you can do next. You have a couple of options, the non-permanent workaround that will fail at some point, and the proper fix.
Non-permanent workaround.
There is a Thrustmaster motor calibration software available at unofficial sources, google it.
In short, you will launch the software and then plug in the wheelbase without the steering-wheel, wheelbase will turn quickly but calmly left to right to left... a bunch of times, and new calibration value will be found. Now wheelbase will have roughly the same rotation speed in both direction.
But... the glue has still failed, so the motor's magnet will slip again, that will throw the calibration off again, and you get it now. For me, at start the wheelbase motor calibration lasted for 1-2 weeks, at the end it lasted for ~30 minutes, before needing to re-calibrate again. And some simracing mistakes will be impossible to pin, was it me, or is the calibration already off. Maybe you will get lucky and calibration will last, maybe, probably not. (Side-note., if you choose to use motor calibration software it should come with instructions, that claim to leave the app running till the calibration is done. But sometime for me the software did not find initial pre-calibration value and the wheelbase slammed violently from left to right, hitting the lock-stops hard. I do not recommend this, the lock limiting bit is made of plastic and also fails. What I did if wheelbase did not calibrate calmly and started the death spin, is simply unplugging the wheelbase, closing all software, relaunching everything, and plugging in again.)
Proper fix.
Simple, reglue the motor's magnet. Problem is, that is not a easy or quick thing. My regret is not taking photos and videos of the process, because honestly, I thought that my T300 is done, and I will make a mistake that is non-fixable. And I was so frustrated with the whole "Thrustmaster experience" that I just did not care to do any extra work. There is a bit of online info out there, several people have done this, it is not easy. If you do this, my recommendation, take your time with removing the inner motor's PCB board, and do not touch the magnet (it is very brittle) with anything hard, lets say pliers for example. I used a wide hose clamp with similar diameter and rubber strip put inside it, so I can grab (tighten the hose clamp around the magnet, do not over tighten) the magnet but not damage it, since I could not remove it with just my hands.
That is what I did. I did 1) then got frustrated with doing 1) over and over again. So I did 2), still have my T300 and have not re-calibrated it in close to 2 years. Now I am very happy with it, do not plan to upgrade soon, but I do remember the annoying time too well, so I get it.
Sorry for making it way too long.
Sorry for not responding quicker.
Hope it helps.
A person with full ThrustmasterTM experience.
