App page property pane follows navigation into unrelated webparts

Target SharePoint environment

SharePoint Online

What SharePoint development model, framework, SDK or API is this about?

💥 SharePoint Framework

Developer environment

Windows

What browser(s) / client(s) have you tested

• 💥 Internet Explorer
• 💥 Microsoft Edge
• 💥 Google Chrome
• 💥 FireFox
• 💥 Safari
• mobile (iOS/iPadOS)
• mobile (Android)
• not applicable
• other (enter in the "Additional environment details" area below)

Additional environment details

Chrome Version 135.0.7049.115 (Official Build) (64-bit)
SPFx version 1.18.0
Node.js version 18.20.4

Describe the bug / error

If you open the property panel on an App page with an SPFx webpart, then close it (or leave it open) and navigate to another page with webparts (custom or out-of-the-box), the App page title and header will appear in the property panel for any webparts edited.

Steps to reproduce

1. Navigate to an App page with a full-page app.
2. Edit the App page to see the property panel. Close it without changes, leave it open, etc - it makes no difference.
3. Without refreshing, navigate to another page with webparts.
4. Edit the page and open the property panels for some webparts. You will see the App page title and the header at the top of the property panel. This happens for both custom and MSFT webparts.
5. If you refresh the page, this behaviour disappears.

https://github.com/user-attachments/assets/f8d79263-dd18-4c84-bc40-20de012d8dd4

Expected behavior

When you open the property panel for a webpart, you should only see properties for that webpart not for previously opened webparts.