Several thoughs:

1. What hardener and at what level did you use it.

2. To see if it is the emulsion + subbing stripping off, you will probably seen a tacky layer on the back side of the emulsion. If there is one, then the emulsion and subbing probably left the support. If there is no tacky layer on the film, then probably both the subbing and emulsion floated away or the subbing stayed in place and the emulsion floated away. Then check the film to see if it has a tacky layer of subbing.

In the case of emulsion + subbing leaving then there is no real adhesion of the subbing. It is the wrong subbing for the film support. If the subbing stays and the emulsion leaves then there is no adhesion of the two and the subbing is wrong for the emulsion.

The one common cure is a different hardener as I said earlier, or a much higher level. Or, you are not letting the coating cure long enough!