This is very similar to #327. (Back then we found out that DynamicProxy sometimes puts a generated invocation type in another module than the generated proxy type depending on it, causing verification failure due to the proxy type module being incomplete. This got fixed in #346.)

It appears there is another case where the same problem occurs, namely proceeding to a class proxy's target from an intercepted protected method. Because you cannot directly call protected methods from outside the target, DynamicProxy does so indirectly via a generated delegate type. Such delegate types can also end up in the wrong module:

public class Foo
{
    public string InvokeMethod()
    {
        return Method();
    }

    protected virtual string Method()
    {
        return "...";
    }
}

var builder = new PersistentProxyBuilder();
var generator = new ProxyGenerator(builder);
_ = generator.CreateClassProxyWithTarget(new Foo());
builder.SaveAssembly();

The last line triggers this exception:

System.InvalidOperationException: Both a strong-named and a weak-named assembly have been generated.