Google Analytics 4 Keep Tracking Multiple Domain

I have more than one domain.

1. DomainC.com - Using Google Tag, GA4, and Google Ads. Installed via Google Tag Manager.
2. DomainW.com - Same with No 1
3. DomainK.com - No GTM and GA4. Only installed gtag.js from Google Ads

Problems:

• Every DomainK traffic is tracked in GA4 DomainC and DomainW.

Goal:

• Make each domain traffic separate from their GA4 account. I don't want their traffic to overlap each other. For example: If a visitor visits DomainW then it's must be only count in DomainW.

What I had tried:

1. Check if GTM is installed correctly
2. Check if MEASUREMENT ID is typed correctly
3. Make sure cross-domain is disabled from Data Stream > Configure tag settings > Configure your domains
4. Testing using DebugView but what I do with GTM doesn't show.

If you need any additional information. Please comment below.

Special thanks to @BNazaruk who give me some clues.

The main problem is because wrong connection in The Google Tag Manager Container.

On the image above, make sure tag name and tag IDs have the correct GA4 ID. I used GA4 MEASUREMENT ID twice in different Google Tags.

Because, when I check to GA4 > Account > Data collection and modification > Data Streams > Configure tag settings.

To prevent this happen again:

Use clear tag names. Don't just use web stream, blog or whatever that doesn't describe the site. Always use prefix or site word to differentiate.