Use attached to reproduce.

Workaround:
class MyDataCellElement : GridDataCellElement
{
    public MyDataCellElement(GridViewColumn col, GridRowElement row) : base(col,row)
    { }

    protected override List<CharacterRange> GetSearchHighlightRanges()
    {
        // return base.GetSearchHighlightRanges();
        List<CharacterRange> ranges = new List<CharacterRange>();

        if (this.ColumnInfo == null || !this.RowInfo.SearchCache.Contains(this.ColumnInfo))
        {
            return ranges;
        }

        string criteria = this.RowInfo.SearchCache[this.ColumnInfo] as string;

        int index = -1;


        CompareOptions options;

        if (this.MasterTemplate.MasterViewInfo.TableSearchRow.CaseSensitive)
        {
            options = CompareOptions.Ordinal;
        }
        else
        {
            options = this.MasterTemplate.MasterViewInfo.TableSearchRow.CompareOptions;
        }

        do
        {
            if (index + 1 >= this.Text.Length)
            {
                break;
            }

            index = this.MasterTemplate.MasterViewInfo.TableSearchRow.Culture.CompareInfo.IndexOf(this.Text, criteria, index + 1, options);

            if (index >= 0)
            {
                var str = this.Text.Substring(index, criteria.Length);
                 
                int symbolCount = 0;
                foreach (char ch in str)
                {
                    if (!Char.IsLetterOrDigit(ch))
                    {
                        symbolCount++;
                    }
                }

                ranges.Add(new CharacterRange(index, criteria.Length + symbolCount));
            }

        } while (index >= 0 && ranges.Count < 32);

        return ranges;
    }
}

private void MasterTemplate_CreateCell(object sender, GridViewCreateCellEventArgs e)
{
    if (e.CellType == typeof(GridDataCellElement))
    {
        e.CellElement = new MyDataCellElement(e.Column, e.Row);
    }
   
}