Intermittent 421 error with tls and HostRegexp router


I use Traefik CE v2.2 depoyed to kubernetes with CRD provider terminating certificates and acting as frontend proxy for hundreds of subdomains.
Our ingress routes are configured with HostRegexp as a catch all rule for all the subdomains of a particular root domain and is properly specified.
The issue is intermittently traefik returns 421 misdirected request.
I know that TLS uses the Host rule to match certificate to SNI hostname. My question is besides HostRegexp, is there another way to create rule that matches wilcard domains?

Thank you all.