Yes, this appears to be a bug, from what I can see. But I wonder if it will work better if the diglot (ALEPH) is the primary project, and it calls PRK as the secondary project.
Presumably you are able to get the original language above when running ALEPH independently, and it is only failing when it comes together with another text as a diglot.
Unfortunately the Archive which was submitted failed to pick up and package the interlinear folder for ALEPH. Would you please send another archive of just an ALEPH interlinear so we can replicate the issue and hopefully solve the problem.