Some WMTS getCapabilities return <MatrixSet><TopLeftCorner> with more than one whitespace as delimiter between the coordinates. This leads to the layer not being displayed, because the origin_ property of ol.tilegrid.TileGrid is not set.
Error in ol.tilegrid.TileGrid.prototype.getTileCoordForXYAndZ_: JavaScript runtime error: Unable to get property '0' of undefined or null reference