Hello Ben Lane,
Welcome to Microsoft Q&A.
Understanding your situation, based on the description, the first issue (unclickable area on the left side of the screen) can be described as a "User Interface (UI) rendering or input processing error" affecting a specific area, and appearing only after using the computer for some time. Below are some possible scenarios:
High probability of UI rendering/overlay issues. Possible situations include:
Transparent window or layer overlay: There might be a transparent or translucent window/layer (part of an application or system component) rendering on the left side of the screen. It might not display any actual content but is intercepting mouse click events. Even if you can't see it, it might be there.
Explorer Shell's GDI/DirectX drawing conflict: As the core of the Windows Shell, Explorer is responsible for rendering the desktop, taskbar, and most of the File Explorer interface. There might be a graphics drawing conflict that prevents click events in certain areas from being correctly passed to the intended recipient.
Other possibilities: Memory leaks/handle leaks, third-party software conflicts.
Driver issues: You might consider reinstalling your graphics drivers. (Ensure a clean uninstall before reinstalling it).
Troubleshooting suggestions for this issue:
Sequentially try a clean boot (this helps isolate interference from third-party software) and Safe Mode (if the issue doesn't occur, it indicates a third-party software or driver is the cause).
Disclaimer: A “clean boot” starts Windows with a minimal set of drivers and startup programs. It helps to determine whether a background service is interfering with your game or program and to isolate the cause of a problem.
These steps of "clean boot" might look complicated at first glance. However, to avoid any trouble for you, please follow them in order and step-by step so that it will help you get back on track.
Create a new user profile: Try creating a new local user account and logging in with it to see if the problem persists. If the new account doesn't have the issue, your old user profile might be corrupted.
Use Process Explorer (Sysinternals): This tool can help you identify which process owns a window handle. When the left side of the screen becomes unclickable, try using Process Explorer's "Find Window's Process" function (a target icon) and dragging it over the unclickable area to see if you can identify the process intercepting the clicks.
Link: https://learn.microsoft.com/en-us/sysinternals/downloads/process-explorer
Second Issue:
File Explorer dialogs (Open/Save) freezing/unresponsive.
Possible network location or cloud sync service issues: When a file dialog opens, it attempts to enumerate recently accessed folders, OneDrive, network drives, SharePoint, etc. If any of these locations are currently inaccessible, respond slowly, or are syncing a large number of files, it can cause the dialog to freeze.
Shell extension conflicts: Many third-party software (such as compression tools, cloud storage clients, PDF readers, version control systems, etc.) install Shell extensions in File Explorer (e.g., right-click menu items, icon overlays). If these extensions are poorly coded or have compatibility issues, they can cause the dialog to become unresponsive when it tries to load them. ShellExView (NirSoft) is a very useful tool that can list and disable all Shell extensions. You can try disabling non-Microsoft extensions first and then enabling them one by one to find the root cause.
Indexing service.
If the first scenario exists, please disconnect all mapped network drives, pause or exit all cloud sync clients, and then test the file dialog. Download and run ShellExView. First, disable all non-Microsoft Shell extensions, then test. If the issue is resolved, enable them one by one to identify the conflict. To rule out indexing issues, you might consider rebuilding the index.
Best wishes
Ami | Microsoft Q&A Support Specialist