Why don't you upload a sample problem pic to Dropbox or similar and post the link here. Then others can see if the problem happens on their configuration.
Yes, I am having the same issue on film scans spotted in photoshop and then worked on in Lightroom. Quitting photoshop (the image was not open...I just did it as a precaution) and then restarting Lightroom seemed to fix it. I have not had this problem in previous Lightroom versions, and I do this kind of thing all the time, as I scan a lot of film in FlexColor, use the content-aware spotting in PS and then work on the final adjustments in Lightroom. I am using a Mac Pro 2013 with 10.9.5. Lightroom is set to write data to XMP.
I posted the same problem just before you did... I saw your XMP work-around and tried it... yes, it works correctly now, however, this should not happen.
Thanks for the hint, it was driving me crazy!!!!
Thank you! Yes, I have exactly the same problem. Since upgrading to LR6, touching almost any slider in the Develop module would cause the image to "reload". Worse, it would often "forget" my previous develop edits: even though they were listed on the History panel, they would no longer have any effect.
Great catch, noticing this was just for TIF files! I didn't make that connection. But as most of my edits involve a round-trip into either PS or Nik, I was almost always editing TIF files. As you suggested, I've disabled "Automatically write changes into XMP" in the Catalog Settings - and now it once again works properly. My first guess was that this had something to do with GPU rendering, but disabling the GPU had no effect on this problem.
This is potentially more than just an annoyance. As mentioned, such a "reload" event would often lose ALL of my previous edits (even though they were still listed in the History panel) and reset the image back to the starting point. That's actual data loss!
A number of people have reported these symptoms. Please add your vote and lots of details to this bug report in the official Adobe feedback forum: BUG: LightRoom 6 TIFF file reloads after each Develop edit, potential data loss
Is this problem occurring when you use third-party plug-ins — particularly Nik?
I checked Nik's site and they list compatibility up to Lr 5. No mention of Lr 6.
If you absolutely need to use these plug-ins, you may want to keep Lr 5.7 on your machine for that purpose?