fetchMoreData with dataReductionAlgorithm set to window in categorical dataview results in error

[WouterBo]

Hi,

I'm attempting to fetch more than 30K rows of data in a custom visual using a categorical dataview. I'm using the 3.4.0 API. Using the example by @dm-p which uses a tableview it seems to work fine. However, in my categorical dataview PowerBI produces an error message saying "can't display visual"..try again later.

My dataViewMappings in capabilities.json look like this:

"dataViewMappings": [
        {
            "conditions": [
                {
                    "value": {
                        "max": 1
                    },
                    "category": {
                        "max": 1
                    },
                    "details": {
                        "max": 1
                    }
                }
            ],
            "categorical": {
                "categories": {
                    "for": {
                        "in": "category"
                    },
                    "dataReductionAlgorithm": {
                        "top": {
                            "count": 1000
                        }
                    }
                },
                "values": {
                    "group": {
                        "by": "details",
                        "select": [
                            {
                                "bind": {
                                    "to": "value"
                                }
                            },
                            {
                                "bind": {
                                    "to": "tooltips"
                                }
                            }
                        ],
                        "dataReductionAlgorithm": {
                            "window": {
                                "count": 30000
                            }
                        }
                    }
                }
            }
        }
    ],

As you can see, the categories are limited to 1000. But the values are grouped by a details field and set to a "window" of 30K. As soon as the user provides the details field, the visual fails with PowerBI giving me the message "Can't display visual".

I realise that the window will apply to the result of aggregation of the data, but it feels like PowerBI doesn't like it. What am I not understanding?

Hope someone can help.

Thanks!

[WouterBo]

So far, I've found that in a Categorical dataview only the categories can have a "window" dataReductionAlgorithm and the values (and eventual group by data fields) should not. They are the ones that result in either "Can't display the visual" or other behaviour. 
It appears as though I can "window" the categories, but the corresponding values are still limited to 30.000 values max.
Any expert insights are appreciated!