Customizing SharePoint List new form via Power Apps not work

I'm facing to an issue with customizing SharePoint list new form using Power Apps. After publishing my custom form multiple times, the new form ist not changed in SharePoint.

Here's what I've done and observed:

• Form settings: The form is set to be the customized form.
• Power Apps preview: I can see the live version in Power Apps, and the weblink and QR code work as expected.
• SharePoint behavior: When I click "New Item" in the SharePoint list, the standard form is displayed instead of the customized one. If I change to SharePoint classic experience (old look & feel), it works. I can see customzed list new form. Reture to modern experience, it shows stardard form again.
• Delay in deployment: After approximately 2 weeks, sometimes 1 monat, the customized form suddenly appears in the SharePoint list with modern look & feel. 

Has anyone encountered a similar problem or have any ideas on what might be causing this delay and how to resolve it? Any insights or solutions would be greatly appreciated!