Can't locate file or assembly even though it is there (Community Toolkit MVVM)

Question

I'm using CommunityToolkit.Mvvm version 8.0.0.0 I'm getting this but only in one part of my project:

XDG0062 Could not load file or assembly 'CommunityToolkit.Mvvm, Version=8.0.0.0, Culture=neutral, PublicKeyToken=4aff67a105548ee2'. The system cannot find the file specified.

It is referring to my using of a property in binding:

 <ComboBox x:Name="cmbPatient" 
                  ItemsSource="{x:Static local:booList.patients}"
                  DisplayMemberPath="fullName" 
                  SelectedValuePath="patientID" 
                  FontSize="30"
                  
                  Margin="5"  Grid.Row="2"/>

It refers directly to the

ItemsSource="{x:Static local:booList.patients}"

This is then related to:

public class myAppSettings
    {
    public static List<Patient> patients { get; set; }
}

and

a model:

 public class Patient: ObservableObject,IPatient

Weirdly though, it runs fine and compiles but as soon as i close the running app the error returns!

I've tried reinstalling but no luck.

I've done the same thing in another app and it doesn't have this issue