"As changes accumulate in the root zone, the difference between the versions begin to matter more. Typical changes in the root zone are changing delegations (NS records), rotating DS records for DNSSEC updates and with all this comes updates to DNSSEC signatures. If the differences remain, then the outdated root server will see the DNSSEC signatures expire and that will begin to have more marked consequences."
I mean, the specific "more marked consequences" are unspecified, but I think "could affect stability" is a reasonable interpretation thereof, and I do personally care that they don't know wtf caused it yet, so...
> On May 21 at 15:30 UTC the c-root team at Cogent Communications was informed that the root zone as served by c-root had ceased to track changes from the root zone publication server after May 18. Analysis showed this to have been caused by an unrelated routing policy change whose side effect was to silence the relevant monitoring systems. No production DNS queries went unanswered by c-root as a result of this outage, and the only impact was on root zone freshness. Root zone freshness as served by c-root was fully restored on May 22 at 16:00 UTC.