I've heard it the first time this season and now we have a report every week.
So if there is no bug, it's very clearly, that sombody changed something in the calculation of the skilldowns.
You do realize the overall player population gets one year older every season (not counting for new draftees), and more importantly the trained-up players are finally well over 30, right? As an example, I have one of my original players/trainees (from season 3), Janne Patteri
(2532493), still in my roster. He is 33 this season and finally experiencing some major skill drops. Even this guy is objectively so bad that I would have gotten rid off him a few seasons ago if he weren't a team legend. But the point remains that you need highly-skilled older players to see major skill drops and for people to care enough about those drops to report them. As the player population has become older, we have now entered that time.