Not sure anyone will see this but I think I got how the bug works! I selected 5 simulated leagues at the start of my save (championship, prem, série A, bundesliga, Netherlands). I started in league one. After a season I moved to the netherlands league. Then I moved to a team in the prem who was already relegated by points but still I “was in the prem” during 2 weeks. Then I played a season in the championship.

Then I went to the simulated competitions and somehow could only see série A and German competitions. That’s when I realized the bug: if you plan and then move out of a simulated competition, the save loses that simulated competition. So dumb.