I got this situation where I have domain https://mail.atec-bb.ch working just fine with Let's encrypt ssl.

and on the other side a newly added domain https://mail.zaflora.cz thats picking up the main domain ssl from Sectigo for domain https://mail.uhlhost.net thats the main domain of my deployment.

Certificate Name: atec-bb.ch
    Serial Number: 37a21540e32a4329c1304631bb7fe0935c6
    Key Type: ECDSA
    Domains: mail.atec-bb.ch
    Expiry Date: 2024-12-17 16:52:33+00:00 (VALID: 88 days)
    Certificate Path: /opt/zextras/common/certbot/etc/letsencrypt/live/atec-bb.ch/fullchain.pem
    Private Key Path: /opt/zextras/common/certbot/etc/letsencrypt/live/atec-bb.ch/privkey.pem

Certificate Name: zaflora.cz
    Serial Number: 34b1a1b6fbb4afe490be8acbdfddb67d579
    Key Type: ECDSA
    Domains: mail.zaflora.cz
    Expiry Date: 2024-12-18 18:15:14+00:00 (VALID: 89 days)
    Certificate Path: /opt/zextras/common/certbot/etc/letsencrypt/live/zaflora.cz/fullchain.pem
    Private Key Path: /opt/zextras/common/certbot/etc/letsencrypt/live/zaflora.cz/privkey.pem

Any ideas what to do to solve this issue?

Inside cerbot certificates both ssls are visible and same in Administration UI. the right certificates are shown.