Several Bugs Appeared after Migrating Purchases to My Main Apple ID

I had a second Apple ID (US) to download apps outside the Chinese App Store. Now that I have moved to Canada, I changed that ID's region to Canada and migrated all purchases to my main Apple ID. However, several minor Apple ID and iCloud-related bugs have appeared on my iPhone.

Here are some bugs I encountered:

• Can't update apps originally downloaded from the secondary Apple ID
  • Every time I try to update an app (e.g. Discord), it'll pop up a window saying "Apple Media Services Terms and Conditions have changed" and asking me to agree to the new terms. Once I agree on them, it'll ask me to verify the secondary Apple ID's password, and it'll fall into an endless loop of verifying the password.
• Windows, like activating iCloud or iMessage, constantly pops up even when I click on agree every time.
• My iCloud storage falls back to 2 TB from 4 TB.
  • I subscribed to Premium tier Apple One and 2 TB iCloud at the same time, and surprisingly, they gave me 4 TB of iCloud storage. After migrating the purchases, the storage falls back to 2 TB, as appeared on the iCloud Settings.

What have I done to try to fix those issues:

• Rebooting my iPhone
• Sign out from the App Store and sign back in again
• Sign out from my Apple ID in Settings and sign back in again.

I have tried all those steps, but none of them worked. I still can't update my apps, and the constant and frequent pop-up windows are annoying. I really anticipate a solution to this rather than just waiting for the next software update to (hopefully) fix this issue. 🙏