Yes, you can roll back to 6.4 but we can probably help you in sorting the performance issues with 6.5.
Could you please let us know what kind of performance issues are you facing with Lightroom 6.5?
Thanks for the help. I've documented the problems I'm having on this forum discussion: Re: "Not Responding" bug is back with 6.5. I hope a fix / suggestion shows up on that thread. In the meantime, I'll roll back to 6.4 and see if that corrects the issues I'm seeing.
Thanks for sharing that.
I would suggest one step here. Go to Lightroom Preferences > File handling > increase the camera raw cache to higher end (may be 80-90GB) > restart Lightroom and then, check the performance.
Chetna, It was worth a try, but didn't make any difference. But I just rolled back to 6.4, and the speed difference is dramatic. I don't know what changed in 6.5, but I hope it gets fixed.