Auto Complete Rules for restricting Manager Type selection

We are trying to restrict users selecting a particular manager type more than once while performing particular actions (Promote/Transfer/Change Assignment).

For Example:

Users can have one HRG & Matrix Manager to their assignment. If anyone tries to add another manager of same type to that user it should allow it to do so.

We tried creating an Auto Complete Rule for this request in which we were able to notify error message when HRG & Matrix Manager was selected to add for an user.

Issue is it is happening for all the actions we perform in manager section. And also it throws this error even if we try to add those manager types for users who don’t have them assigned already.