It's definitely curious how it seems to trigger at about exactly the 5 year date. Do you have service time limits set on your minor leagues? I don't imagine it should cause this, but there may be something causing teams to somehow be strict on what they are doing on these players.
In any event, I would suggest if you can upload your league file (
https://support.ootpdevelopments.com...p-developments) and we can investigate what might be triggering this.