Manni,
I agree that Koker was not in the POW camp as he was only a POW for 24-30 hours. From corresponding with his son, I do have a "theory" on where that story may have come from.
I have also been working on the route of Hopkins’ flight.
They flew the same route the BG took to the target at Aschersleben at the which they tried 3 times to bomb.
Then they flew on to Gusten (about 7 kilometers ENE further on) to bomb location rD670630, which they described as a rail “choke-point”. Again, they could not bomb as the PDI in the lead plane failed. That location translates via echodelta.net to 51.80357N, 11.6096E . That precise spot is the middle of a field, but about 200 meters to the south there appears to be the remains of a railroad overpass, with what was one pair of tracks going north by crossing over via the overpass another pair of tracks going roughly to the east. Today it looks like the tracks going north now end at the overpass and only the railbed is visible further to the north.
Here is the location on Google Maps.
Location of rail over-pass: 51.799806, 11.608472
You can zoom in and out and drag the map around to see the target.
https://www.google.com/maps/place/51...1!4d11.6084721