[exim] IPv6 lookup issues what am I doing wrong?

Hello,

Using exim 4.92, I have a couple of IPv6 configuration issues I hope someone can help with.

The following works fine for IPv4, by that I mean it sets the smtp_active_hostname correctly for all IPv4 interfaces. However, it does not work for IPv6
smtp_active_hostname = ${lookup{$received_ip_address}lsearch{/etc/exim/smtp_active_hostname}}

I have even tried changing the separator in the file to ; and the lookup to
smtp_active_hostname = <; ${lookup{$received_ip_address}lsearch{/etc/exim/smtp_active_hostname}}

I know the $received_ip_address is populated correctly because crude debugging (log_message = $received_ip_address) shows the correct IPv4 or IPv6 address.

I have a similar issue with
tls_certificate = /etc/exim/$received_ip_address.cer
tls_privatekey = /etc/exim/$received_ip_address.key
tls_dhparam = /etc/exim/$received_ip_address.dh
The certificate is found for IPv4 connections, but not IPv6.

Can anyone point me in the correct direction to fix the issues.
Any help would be much appreciated.

Many thanks,