CoreDNS 1.8.3 not supporting while upgrading AKS version 1.19 to 1.20. or 1.21

we are upgrading our on prem IBM APIC verison from 4.1.15 to 4.1.17 along with AKS 1.19 to 1.20. because our aks version1.19 is going to expire in oct,2021. we tried to upgrade and downgrade our coredns 1.8.3 to 1.8.4 and 1.8.0-1.8.2 but after 5 min for that verison came back to 1.8.3 it self.

below is the warning message it shows in pod logs.

Warning: (DNS ISSUE?) We have not started up yet, and we are not declaring readdy, but our pod is showing up withing the ( pod )service
Warning: (DNS ISSUE?) If you are using coredns >=1.8.1 to <=1.8.3, there is a known coredns bug which will the portal pods from starting.