I *think* I can't recommend 1984.hosting for secondary DNS if you use DNSSEC at the moment. It *appears to me* they don't replicate/refresh the RRSIGs. So I **assume** they simply check the SOA serial and only fetch the data if it changed.
Don't you love it when #DENIC says "UPDATE FAILED", because you have to edit *your own zone's* NS entries *first*, and only then go to your registrar to edit the nameservers there.