Hello together I took over the above mentioned vehicle a few months ago with a transmission damage and in the last weeks the transmission was re-stocked and the transmission output shaft replaced (running surface for shaft sealing was damaged during removal). As was shown during the repair, the scooter was last moved without gear oil. The gears looked still intact for me, therefore I did not replace the input shaft and the intermediate wheel. After the repair is l The sound is audible in the attached video. During the repair I took some photos, without focusing on certain details. I also attach the most meaningful photos. What could be the most likely cause of the problem with this description/documentation? I am not sure if I am able to get the most out of it.