Photoshop 2019 / 2020 on Windows laptop lagging - no CPU or Memory overuse - wacom cintiq

Switching tools, ctrl-z, zooming, using the click-drag for the hand tool (shifting the canvas), and using the eraser tool causes Photoshop to lag and sometimes to freeze. Brush tool usually works fine but sometimes has some lag if I have just done one of the items above. This has been happening since I switched to a new laptop and started using it with an old Wacom Cintiq (approx 10 years old).

Laptop specs:

Processor: IntelCore i7-8850H CPU @2.60GHz 2.59 GHz

Installed memory (RAM): 32.0 GB (31.6 GB usable)

475GB SSD with 163GB free

When I check the CPU and Memory usage while I'm using Photoshop, the CPU usage never goes over 5% and the memory usage never goes over 22% even though Photoshop is lagging and freezing. Plus, I have recently noticed that there is a difference between using the trackpad and built-in laptop keyboard versus the cintiq and a USB keyboard.

It's a new Lenovo Thinkpad P52, so it should be able to handle Photoshop. It handles Premiere just fine. I'm using it with a Wacom Cintiq 12WX (DTZ 1200w), sometimes an old Wacom Bamboo as well. Does multi-Wacom use cause problems? Or the age of the wacom? It does not have problems with other programs (e.g., it works fine on Premiere).

I also create and use most of my files within a Dropbox folder, but Dropbox should only interfere with saving -- and the files never have problems saving.

I'm at a lost! I've tried reseting the preferences, unchecking "use graphics processor", checking it again, letting photoshop use more RAM, increasing the cache levels, decreasing the cache levels, decreasing the history states... I'm not sure what else to do!!

Any tips or advice??