I've recently encountered an issue with the Web AppBuilder for ArcGIS Filter widget not saving when I change "Display features in the layer that match all of the following expressions" to "Display features in the layer that match any of the following expressions".
I can change this option and navigate through the different layers to add additional expressions but when I click OK, exit and open the widget back up, that drop down reverts back to "all of the following" for every layer.
I seem to be able to change (and save) the drop down that is located under the "+New filter" though.