Hello,
Yesterday I changed my journey to Ultimate Strength. All my skill progressions was valid. For example, I was 4/4 on pullups and 2/3 on strict muscleups. When I checked today my pullups progress on 1/4. So I am not receiving pullup movements anymore, hence my muscleup option is gone.
I’m mastering these skills for such a long time and pullups was just a example.
Is there any bug or something am I mising?
What Training Journey were you on previously?
No need to answer this, I’ve taken a look 
First thing, as has been answered a few times elsewhere; In any new training cycle you can get asked to do Skill milestones that you might already have completed previously, particularly if you have not worked on them for some time. Even professional athletes spend a lot of time working on the technique of simple exercises that they have long since mastered.
If you have every skill progression enabled, progress on skills is slower, and you are probably more likely to loop around as the chances of not working on a skill is higher.
It doesn’t affect the Coach assignment of the session, only the Skill Progression assignment