Back in early days of ASL there was only one registration server when ASL was smaller and there was no need to turn on dnsmgr in asterisk.
(Legacy node owner this pertains to your old Allstarlink nodes that have been running for years.)
Recently, because of the growth of ASL over the last few years we have had to add more registration servers to balance the load that was being put on one single server trying to handle more than 3500 nodes all trying to register. Lately, we have been seeing issues with some users registering. I believe these are Legacy nodes owners and are having issues because they do not have dnsmgr enabled for their nodes.
See the link on the wiki. https://wiki.allstarlink.org/wiki/Dnsmgr.conf
Enabling dnsmgr might help solve your node registration problems.
Basically if you enable dnsmgr, if one of the three registration servers goes down, your node will look for another registration server to register too.
There are three servers, SEA, ORD and CQF, so there is a pretty good chance that your node would be successful registering with another server if one is down or not working correctly.
Marshall - ke6pcv