With who / where are your DNS records maintained? 1&1 IONOS? / Plesk? / Another Option? Removing all the AAAA records might be a workaround for now, but that's not fixing the real problem
As mentioned, we too have IPv4 and IPv6 server addresses, so obviously we have both A and AAAA records (plus many other DNS records) We're also with 1&1 IONOS and using Let's Encrypt certificates (some normal, some *wildcard, some multi-domain etc). Pretty sure it's unlikely to be either a 1&1 IONOS or a Let's Encrypt directly related issue. Surely it can only be a server setup / setting glitch somewhere?
Edit: One quick check meantime, actually within Plesk;
Do you have both IPv4 AND IPv6 addresses setup correctly in here:
https://**your-FQDN**:8443/admin/ip-address/list/