Problem in Setting Specific Notification Sounds for Individual Contacts: Redmi Note 11 Global

Hi !
I use distinct notification sounds (as well as ringtones) for 5 of my contacts. Remaining all contacts use default notification sound and Ring tone. Every thing was working fine till yesterday when I changed the default notification sound and default ringtone of my device. After that the specific notification sounds were changed to default whereas the specific ringtones continued working fine.

PROBLEM : Now when I try setting distinct notification sound of any of those 5 contacts it changes the sound but set the same sound for all five contacts. The latest specific notification sound set for any of contact become the notification for all contacts with specific notification sounds. Contacts set for default notification sound keeps working as desired.

I searched for the problem on internet and as per the guidance I deleted the data of "messages app". That did not delete my messages as claimed but reset notification sound of all contacts as default. However when I set the distinct notification sound for those 5 contacts the problem persisted as before ... that is ... The last specific notification sound set for any of contact become the notification for all contacts with specific notification sounds. Contacts set for default notification sound keeps working as desired.

I have been using this feature on android phones for many years but never encountered such problem .... Please suggest a solution !

Regards
Sheeba