i am experiencing the exact same issue for 24 hours now.
Error: An unexpected error occurred. If this issue continues, contact support.
When can we expect this to be resolved?
In order for me to set a 301 redirect, I had to first change "Nameservers" (under Manage DNS) from "Custom" to "Default". Once saved, I was then able to successfully apply the 301 forward/redirect. Good luck!