SPFx WebPart fails to load on Classic Page Recently with new instance.

Target SharePoint environment

SharePoint Online

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

💥 SharePoint Framework

Developer environment

None

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

• browser version
• SPFx version
• Node.js version
• etc

Describe the bug / error

Adding a new SPFx WebPart to a classic publishing page in the Pages library of a SharePoint Online site results in a runtime error. Existing classic pages with SPFx WebParts still work,new instance and old instance in Modern page still work and even the same SPFx WebPart continues to function if it was already present before the issue appeared. However, adding the same WebPart as a new instance on the same page now fails systematically.

Steps to reproduce

1. open SharePoint online classic page
2. Edit page and add any SPFx web part which is working in same site on different/ same page
3. Save the page.
4. You will see the error

Expected behavior

Web part load and I should see the content.