First you need to decide which problem you want to solve. Selling Aperture and moving to Lightroom will lose all your raw edits and much of your metadata. Thats's potentially a lot of re-work, so it's only really worth doing if you decide you prefer LR over Aperture.
If you decide you want LR then concentrate on the move.
If you want Aperture then concentrate on understanding and resolving the issue.
If the issue turns out not to be fixable, you have the option to move to LR, revert to Aperture 2, or perhaps other work flows.
To start tracking down the issue, do some of these:
1. Make sure you have installed all firmware updates for your machine (especially gfx card).
2. Download the stand alone version of the latest software update and re-apply it.
3. Repair permissions.
4. Start Aperture and leave it for a few minutes to see if there are any background processes trying to run (thumbnails, previews, internal processes, faces, places, etc). If there are, leave Aperture running them until everything is complete.
5. Try scrolling through a view of all your images, the thumbnails should appear quite quickly. If you see that it has to generate thumbnails, this is a sign that a process got cancelled (by you, by quitting Aperture, or by Aperture crashing). If this happens, select all images and choose the option to regenerate thumbnails. Leave it (possibly several hours) until it completes.
What you are trying to get to is a reliable installation of OSX, on reliable hardware/firmware, running a reliable Aperture database.
6. Once you are confident Aperture is not running any background processes, quit Aperture. Use first aid (press option + command while launching Aperture) to repair permissions. Then again to repair the database.
7. Create a duplicate version for the image showing corruption. Process it but turning one of the adjustments off and then back on again. Does it still corrupt.
8. Create a duplicate version for the image showing corruption. Re-process it using the new raw engine (press the button shown in the raw section on the screenshots you posted in your thread). Does it still corrupt.
Try launching Aperture in 32 bit mode and repeat 7 & 8. Does it make a difference.
Try booting your Mac with the 64bit kernel (hold down 6 and 4 while booting). Run Aperture in 64 bit mode, Does it make a difference.
I used to get a similar problem in Aperture 2, once Aperture had been running for a long time and the GPU got very hot. I think the OS throttles back the GPU to reduce heat and that seemed to introduce the issue. If you leave you machine off until cold, and then process the images, does the corruption still occur.
If you think people with LR or Capture 1 or Bibble don't ever get problems, take a visit to their support forums.
-Najinsky