Hi @turnleft
The issue appears to stem from misconfigured DNS. It appears the old NS records are still present alongside the Netlify records
seaslug.se. 3600 IN NS ns60.domaincontrol.com.
seaslug.se. 3600 IN NS dns1.p01.nsone.net.
seaslug.se. 3600 IN NS dns2.p01.nsone.net.
seaslug.se. 3600 IN NS dns3.p01.nsone.net.
seaslug.se. 3600 IN NS dns4.p01.nsone.net.
seaslug.se. 3600 IN NS ns59.domaincontrol.com.
You need to remove the two domaincontrol.com NS records. You do need to ensure any other records (e.g. MX, TXT) are in Netlify DNS first. See [Support Guide] How do I migrate a domain to Netlify DNS with zero downtime?