On adding the first static DHCP I got the error below. Not really a problem, since the static dhcp lease is indeed registered. The error could possibly be prevented bij creating an empty file on install or something.
So its a false positive error, not really a problem but solving this makes pihole a bit more neat.
Expected Behaviour:
Info: A new static address has been added
Actual Behaviour:
There was a problem applying your settings.
Debugging information:
PHP error (2): fopen(/etc/dnsmasq.d/04-pihole-static-dhcp.conf): failed to open stream: No such file or directory in /var/www/html/admin/scripts/pi-hole/php/savesettings.php:66