"Reading" not retaining

I've noticed this on and off, and again just today: Files in my "Reading" bin disappear over time. In the case today, one I was just reading yesterday was gone. It was still marked as being read in the comic folder, so the database knows it's being read.

Where do you have your comics located? In a NAS maybe?

They are on a different drive, but on the local system. Like I said, they are still marked as read then I look them up in the library, so they only get lost in the Reading folder.

One theory I had is that just opening to the cover is not enough to keep it on Reading. I'm going to try an experiment by opening 12 titles, and see what happens to them over the week. Attached is an image of the 12. I'm only reading the two Spiderman titles actively, the rest are ones I opened randomly, and won't touch. As a control, the Irredeemable and Incorruptible were only opened to the first page, and the rest I went a few pages in.

I have YAC installed on C:, and all my comics are F:, a standard SATA drive.

Yes, the "Reading" list only selects comics that have been opened, they are not finished, and the reading is progress (current page > first page).