1150GS Gearbox Problem

[Kinobi]

Greetings from Italy. I live up this tread because I cannot see the images attached. Due to a Clutch replacemente (leaking clutch slave) since then, once in a while only upwards, from 2 to 3 the gearbox it simply does not switch. I need to go to 1 and then it works. I tried to fix the gear lever, but it did it again. The bike performes well except that once in a while it does it. Genuinely speaking, we put Castrol gear oil mineral instead of the MTX 75W140 and once I re put the MTX, it did not do it for awhile. I was wonder to what you were referring to the Haynes manual, but I can't see the photo (I have the manual). Can you at least tell me the pages? Thank you.
What else to check beside removing the gear lever and place it again?

 

[Cyrano]

The chapter about the gearchange lever is on page 5.4 of Haynes Manual.

 

[Kinobi]

Thank you.
Unfortunately all is tight. Lever and all bolts.
I read this topic too: https://www.ukgser.com/community/threads/sloppy-gear-lever.14577/
Any clue what else can be?