I assume you're using DevExpress controls in WinForms, but without specifics I can offer only some general advice.
The leave/lost focus event on a UI control will also trigger validation, which if the DataSourceUpdateMode is OnValidated will also try to push changes to the data source. Changes to the entity will trigger INotifyPropertyChanged, which will cause a listening UI control to refresh and possibly call TypeDescriptor.GetProperties in doing so. This GetProperties call is usually the culprit behind any type of unwanted/unexpected property retrieval, since the getter will be called for all properties, including navigation properties. I know you said you have a selection list, but some UI controls will think the data has changed even when it hasn't (because of parsing/formatting/masks). If using a data or list converter you can set the Editability to ReadOnly to ensure property setters aren't unintentionally being called.
If you can't track down why TypeDescriptor.GetProperties is being called, other options are to data bind to a "wrapper" type which contains only the properties of interest or use a dynamic type; or if it makes sense, pre-load cache with the related data so that calls to the datasource are not made.