Try unchecking the option Preferences > Performance > Use Graphics Processor. LR's performance in Develop can be dodgy when it tries to use low- and medium-performance graphics chipsets, and its behavior on such chipsets can change with every release as Adobe changes the code utilizing GPUs. Unless you have a 4K or 5K display, most people report that enabling the CPU results in little or no improvement. See here for more details: Adobe Lightroom GPU Troubleshooting and FAQ
If disabling the GPU helps, then you could spend the time to ensure you have the most recent graphics driver from the chipset's manufacturer (see the FAQ above).
GPU is already unchecked. I am just using integrated graphics, so there isn't any GPU support anyway. But I'm wondering. My wife tried taking some handheld panorama images yesterday. And those stitched images are what seemed to be slowing down my Lightroom performance. Lots of jagged edges. It was her first time trying panorama shooting, and I just let her experiment. Do you think those irregular edges that are still there even when the image is auto cropped could be impacting Lightroom performance? It seems that working on single images works OK. And when I have done panoramas I have always used a tripod so there isn't as much irregularity.
Do you think those irregular edges that are still there even when the image is auto cropped could be impacting Lightroom performance?
It's possible -- but I don't recall seeing any similar reports. It could be just the size of the panorama's DNG that's stressing your system -- they can get pretty big in pixel dimensions. I'd be surprised if modest cropping of the edges affected the issue (other than reducing the total number of pixels being edited).
How large is the panorama? If it is many images, you can expect some slowdown loading the image and doing filters and brushing in Develop depending on the machine. An i5 with 8GB of RAM will definitely have some issues with really large panos.