I use a custom filter row for the Grid where I have added a custom component holding the filter cell content. I am saving the Grid state upon change and restoring it on initialization.
I noticed that the custom filter component is initialized before the Grid state. As a result, there is an applied filter but the input in the custom filter component does not show it.
This behaviour was new since version 6.0.0. With 5.1.1 it doesn't appear.