Donald Qualls
Subscriber
The DF worked fine with the next roll of 'normal' film. So I guess just BW400CN is the issue.
Given this film was discontinued years ago, it's probably a moot point, but I can't see how it can have enough halide to create the dye image for C-41 without leaving a silver image in any B&W developer and fixer (including monobath). Something very strange happened there.