The catalogue of compositions by Bach has some appendices, in German called Anhang. This trio on the hymn 'Herr Christ, der einig Gottes Sohn' is part of the Anhang II, which contains works of which isn't certain that Bach composed these works. The manuscript of this piece doesn't indicate a composer. However, the complete manuscript is written by Johann Ludwig Krebs and consists of many works which are actually written by J.S. Bach. I'm not sure if this could be a Bach piece and I will never be sure. Bach has presented it with an oeuvre which shows a lot of variety and surprises. The quality always remains, which is also present in this fine chorale trio.