Hello Lukas,

Indeed there is a bug but is a bit different. I have changed the title as actually the issue is caused by the fact that the HighlightDeletedRows="true" is set, meaning that the record is not automatically deleted but an Undo button is added. 

The actual issue is due to the fact that the Undo button is added to the first cell by default and the positioning styles are incorrect when the first cell is edited, which makes the cell's position relative instead of static.

The following script can be used as a temporary workaround:

var old = Telerik.Web.UI.GridBatchEditing.prototype._createOverlayDiv;
Telerik.Web.UI.GridBatchEditing.prototype._createOverlayDiv = function (rowElement, tableView) {
    var $rowElement = $(rowElement);
    old.call(this, rowElement, tableView);

    $overlayDiv = $rowElement.find(".rgBatchOverlay").eq(0);
    $rowElement.find("td").not('[class*="rgBatch"]').eq(0).append($overlayDiv);
}

As a small token of gratitude for helping us identify this issue, we have updated your Telerik points.

Regards,
Peter Milchev
Progress Telerik