A Grid doesn't sort if sorting column cointans a dot in the PropertyModel of the Grid. 

if ((paginationModel == null || paginationModel.getSortColumnId() == null)
|| !(dataModel.getPropertyNames().contains(TapestryInternalUtils.extractIdFromPropertyExpression(paginationModel.getSortColumnId()))))
{return Collections.emptyList();}

if (paginationModel == null || paginationModel.getSortColumnId() == null
|| dataModel.getPropertyNames().stream().noneMatch(x -> TapestryInternalUtils.extractIdFromPropertyExpression(x).equals(paginationModel.getSortColumnId())))
{
	return Collections.emptyList();
}

public class A
{
public B b;
}

public class B
{
public name;
}

public class C
{
public BeanModel<A> getGridModel()
	{
		final BeanModel<A> model = beanModelSource.createDisplayModel(A.class, messages);
		
		model.include();
		model.add("b.name").sortable(true);
return model;
}
}