Incorrect error using static local function

I have several local functions which do not capture any state, and which Visual Studio tells me can be converted to static local functions.

In most cases, R# seems happy with this. However, in one specific local function, R# incorrectly generates an error: "A static local function cannot contain a reference to 'this' or 'base'".

There is no such reference in the function. The code compiles and works as expected.

public IReadOnlyList<ChartItem> LoadChart(...)
{
    ...
    static IReadOnlyList<ChartItem> SumFirms(IEnumerable<(decimal b0, decimal b1, decimal b2, decimal b3, decimal b4)> firmResults)
    {
        decimal b0 = 0, b1 = 0, b2 = 0, b3 = 0, b4 = 0;
        foreach (var item in firmResults)
        {
            b0 += item.b0;
            b1 += item.b1;
            b2 += item.b2;
            b3 += item.b3;
            b4 += item.b4;
        }

        return new List<ChartItem>
        {
            new ChartItem
            {
                Label = "Band 1",
                Color = new ChartColor(128, 198, 85),
                Value = b0,
            },
            new ChartItem
            {
                Label = "Band 2",
                Color = new ChartColor(245, 185, 63),
                Value = b1,
            },
            new ChartItem
            {
                Label = "Band 3",
                Color = new ChartColor(237, 129, 52),
                Value = b2,
            },
            new ChartItem
            {
                Label = "Band 4",
                Color = new ChartColor(233, 97, 46),
                Value = b3,
            },
            new ChartItem
            {
                Label = "Band 5",
                Color = new ChartColor(255, 46, 46),
                Value = b4,
            },
        };
    }
}

VS2019 v16.3.6
R# 2019.2.3