After researching more about ktm 790/890/901 cam failures, i found something interesting in the shop manual, check out this video to find out.
please check out these videos and support them
https://www.youtube.com/watch?v=MSS27hsgPkg&list=WL&index=3
https://www.youtube.com/watch?v=soqcC8nB0-w&list=WL&index=4&t=3s
https://www.youtube.com/watch?v=3O-nySmIYFk&list=WL&index=5&t=1s