Nope, I have not tried other settings above 300 seconds, but every 60 seconds worked.
I have sent D-Link Support a message (CSP15114515) 1-2 weeks ago, but they send from an email address that can't be replied to: "This e-mail message was sent from a notification-only address that cannot accept incoming e-mail".
I did try to register on the online support portal, or whatever it was called, to reply there, but my I never received the email with my password (I tried several times, and use searched in Spam on Gmail, etc). So, unless someone from D-Link support reads this post, it will never be solved.
I am not going to waste more time by calling them too. I will just use the 300 seconds, and see if D-Link bothers to fix the bug at some point. That would be a nice, big surprise.