Here's an example of what I'm now getting almost 100% of the time when using Generic Preselection. I have uploaded the test files and the batch.xml here:
https://www.dropbox.com/sh/vq9871ija9we1r4/AADT5ajSgePUN1A-e5X9xpNJa?dl=0In the screenshots you can see what looks like a flap going diagonally thru the main part of the scan. Sometimes it's diagonal like that, while other times it's almost parallel. If I run this exact same test through 1.7.3 with Generic Preselection it works fine, but on 1.8 it does this. Turn off Generic Preselection and it comes out fine.
Like I said before, this just started doing it a few days ago. I never had this happen with 1.9 using this same Batch previously.