I did not experience crashes or problems with presets after updated to LR 7.3 earlier this month, but I did have performance issues, the most annoying of which being that LR would beach-ball for several minutes after being launched, although not consistently (i.e., sometimes it would launch just fine). Another thing that bugged me is that it would take several seconds for the adjustments to be reflected on my primary monitor, even though they seemed to show up almost instantly on my secondary monitor.
I was excited to see that Adobe released a 7.3.1 update with bug fixes, and installed it right away. Boy was that a mistake! Not only did the update not solve these two issues, but it managed to corrupt my catalog! When I first launched it, it said that the catalog needed repairs. So I clicked OK, and had it attempt to do the repairs, only to be presented with a dialog box telling me that the repairs could not be performed and that the catalog is corrupted. Fortunately I had a recent backup (manual) and was able to get that one to work. But the beach balls and slow updates on the primary monitor persisted, even with a new test catalog I created for troubleshooting. And this morning, upon waking my Mac, I was greeted with a dialog telling me that LR had quit unexpectedly!
I'm going to be going back to LR 7.2 as soon as I get home tonight. The question I have concerns the presets. I keep reading that 7.3 uses a different preset format (xmp). Are my old format presets still there, or are they lost forever? I have some backups, but I created a bunch of new ones not too long ago and those were not backed up.
Very disappointed with Adobe. If I knew my latest catalogs would work with LR 6, I would get that so I could still access the work I've done to this point, and get Capture One for everything I do going forward. Dropping Photoshop is the next logical step after that. I use it mostly for panoramas, perspective adjustments and retouching, and rarely do any compositing or even simple stuff with layers. I'm sure there are other tools that do a half decent job for these types of tasks. Yes, this will cost me in the short run, but I don't cherish the idea of paying rent to Adobe for a closet in crack house!
Can you check whether physically disconnecting the secondary monitored helps to stabilise things?