Internal Error with netcup and DNS Challenge

Describe the bug
I want to access my internal password management (vaultwarden) with NPM. Therefore I created in Netcup an A-Record with Destination my internal IP 192.168.178.15. Also I added a TXT entry with Destination: pw-local.MYDOMAIN.

In NPM I created a proxy host and Forward to my password management. In SSL I want to create a certificate with Use a DNS Challenge. I selected netcup as the provider and set dns_netcup_customer_id , dns_netcup_api_key and dns_netcup_api_password. After save I get a Internal Error Message.

In Docker Logs I see

[12/30/2021] [4:20:50 PM] [Express  ] › ⚠  warning   Command failed: certbot certonly --config "/etc/letsencrypt.ini" --cert-name "npm-47" --agree-tos --email "MY-EMAIL" --domains "pw-local.MYDOMAIN" --authenticator dns-netcup --dns-netcup-credentials "/etc/letsencrypt/credentials/credentials-47"

Saving debug log to /var/log/letsencrypt/letsencrypt.log

Inside letsencrypt.log:
"Incorrect TXT record \"pw-local.mydomain.de\" found at _acme-challenge.pw-local.mydomain.de",

Nginx Proxy Manager Version
2.9.13

Operating System
Ubuntu 18.04.4 LTS (Bionic Beaver) with Docker

Edit: If I add the domain to an other proxy host in NGINX the website can be opend but of couse with an certificate error.
Without a certificate it is not possible to access the website.

Reproduce the DNS Challenge flow with Netcup using the reported Nginx Proxy Manager 2.9.13 setup, then inspect the Docker output and /var/log/letsencrypt/letsencrypt.log. Trace why the _acme-challenge TXT value is reported as incorrect; done means the challenge succeeds and a certificate is issued without the Internal Error.