Hi Gabby,
Welcome to Microsoft Community.
Thank you for providing detailed information about the issue you are experiencing with your Surface Pen. Based on the troubleshooting steps you've taken, it appears that the problem is not with the Surface or the software, but with the Surface pen's hardware.
I understand that your Surface Pro 5 doesn't meet the requirements for Windows 11, but consider that Microsoft’s support for Windows 10 ends in October 2025. If the pen problem persists and performance degrades over time, it might be worth considering an upgrade to a Surface device that supports Windows 11 for improved features and compatibility.
If the pen works fine in other programs like Krita and Whiteboard, then it could be a Photoshop-specific issue that’s not related to hardware. But if it's still problematic across all apps, you may want to consider getting a repair or getting a second opinion from Microsoft support. Contact Us - Microsoft Support
Your SincerelyHahn. W - MSFT | Microsoft Community Support Specialist