If you are going to do a lot of cloning/healing on a single photo, then this is an unavoidable problem in Lightroom.
Some ways to help:
- do the cloning as the next to last step on a given photo; and the last step is to apply lens corrections
- do the cloning in Photoshop or Photoshop Elements
- get a faster CPU
My opinion (I do not work for Adobe) is that large amounts cloning and brushing on one photo push the limits of this non-destructive editing technology beyond the point where the hardware can handle it.
I use ssd drives, 16 gigs of ram, and an 8 core 3.6 gigahertz processor. I know that is far from the best, but that should be fast enough. The reason I don't jump over to Ps is the time it takes to jump over. I retouch hundreds of photos at a time. A little bit of time on each photo ads up. thank you for your input
SSD is irrelevant, memory is irrelevant, the only thing that will help is a faster CPU.
I'm not tech savvy enough to know what is "relevant" I was just explaining what equipment I was using.