I have been experiencing terrible lag when attempting to use the abjustment brush. In fact it has made the tool completely unusable. I have read through various support threads both here and elsewhere and tried all of the recommended changes, from restrictinf the video cache, turning off loop previews, not writing to XMP, and pausing syncing, etc. but to no effect.
I am running the 10.2 release of LRC on my high-end macbook pro (specs below)
I have tried a lot of different things but nothing seems to affect this issue.
It may be worth noting that I am having a similar problem with the brush tool in photoshop as well.
The size of the image doesnt seem to have any impact on this issue. Most of my images are coming from my 5D Mark IV and are 6720x4480. But smaller images coming from my phone, or even images cropped down to 1440px or smaller all experience the same issue.
It also does not seem to matter if I am wokring only on my laptop screen at 1680x1050, or if I am connected to my external monitor at 3008x1692.
I have seen some posts claiming to have seen this issue be impacted by being connected to a USB hub, but I have not found that to have any impact either.