Transalp PD06 BJ 94 chain jumps

Hello, at my Transalp the chain jumps. I have made a video for it. https://youtu.be/1qO4g-KYmyg?si=IGxAdg4TJ–M808h I can exclude the chain tension. No matter if I loosen the chain or put on something the chain jumps on. I also cleaned and oiled the chain. I think it almost comes out of the engine. Something in the engine stops thereby the pinion is slowed down and the chain jumps thereby. I am not sure. The motorcycle runs normally. I have also shot a video without a chain, only from the pinion. https://youtube.com/shorts/wyyFz-qttUI?si=oTDhYw3_uyVSWNW5 I would say that the motorcycle switches and runs correctly. It becomes particularly clear when I brake off and speed up again in the first or second gear. Then it really clatters from below, which I also notice partly on the footrests. Probably also the other gears. but I don’t notice it that way. I am currently driving through West Africa. the motorcycle i You’re always loaded and exposed to a lot of dust and dirt.