Wrong image preview while I am moving adjustment sliders in Aperture

Thanks for the suggestion... but generating new previews and forcing new previews does not solve the problem. Also to be clear, the correct image appears until I grab the slider and the wrong image appears for the duration that I hold onto the slider and then reverts back to the correct image with the new adjustment. Stranger still, the incorrect preview demonstrates the adjustment I am making yet that image (correctly) remains unchanged when I go back to view it.

I have rebuilt the library once since this problem began with no success. I have also done a repair and permissions repair with no improvement.

Another feature of the situation is that the only "wrong" images that appear are ones that I have just adjusted and not other images in the project.

The referenced files are on an eternal Promise Pegasus2 R4 8TB RAID connected via thunderbolt 2

The library is on the boot 1TB internal PCIe flash drive (I thought this would be faster than the external)

Sorry, I misunderstood about that but I have now tried regenerating the thumbnails also and have discovered more... When I edit in a split viewer is when the problem occurs, when I use the viewer only the problem dissappears. When I return to the split viewer sometimes the problem goes away but sometimes not. That is also the case for generating thubnails, it soemtimes relieves the problem temporarily but it still returns.

It really seems that somehow Aperture is referring to a cached image from a image when I attempt an edit. Another guess is that it may have something to do with Mavericks memory manager trying to guess which images to hold in memory and which to release. I can still get work done but this is disruptive to my workflow when I have to keep switching views in order to make a quick edit.

Thanks for te help so far and let me know if you have any othe ideas.

Yes the drive is formatted OS Extended (Journaled) but the library is referenced not managed. I do not keep a clone of the drive but maintain backups of all the data on a separate NAS drive.

I am using the internal 1TB PCIe based flash boot drive for the library and only use the external drive to store the referenced images.

I am using the NAS as a backup. The main storage for my images is the thunderbolt connected Pegasus2 R4 disk array. The Pegasus is always connected and is running whenever the computer is active.

I thought the thumbnails and previews were stored in the library. If that is true, the external drive should not be a big factor. It is true that the images must be available if adjustments are being made but only to reference the original image data which remains untouched.

Finder indicates the correct file whether or not the image in the viewer is viewing correctly. Lately I sometimes also have a previous view of the same image show up while I am making adjustments. For example, if I zoom in on a part of an image and then zoom back out and make an adjustment, the zoom view shows while making the adjustment.