As I recall from the last time I changed my fuel filter, the Bosch filter is supplied with two new copper rings for the banjo bolt - could be one was removed. Talk to your supplier.

The old rings can be reused. You will notice that the sealing surfaces are galled. Place a piece of 220 to 400 paper on a flat surface and wet it with mineral spirits. Then dress both sides of the copper seal rings until the galling is removed and the surface is flat and smooth.

This technique can also be used to get several uses from the oil pan plug copper seal ring.

Duke