Expiring Validity Date Error

I am trying to expire the old framwork in my Master Data and have been able to expire the old risks, objectives, controls, subprocess, processes, etc. However, in some subprocesses, I get an error that states “Change of validity not possible because case exists or in a policy”. I’ve checked the policy and cannot find that it is assigned to a policy. If I am able to expire the control under that subprocess, why am I not able to expire the subprocess?