I have the X1 extreme gen 5 which is considered to be the “sibling” of the P5. I had the same problem and put trouble shooting steps in my HCL report. Check out the “Integrated GPU Screen Tearing” section.
I would also check the display setting in the bios. There might be an option to increase the integrated gpu memory. I increased mine to 512MB which helped a lot!
Report: Thinkpad X1 Extreme Gen 5