zone event load failed
I have two knot instances A&B fetching axfr/ixfr from the same upstream C, and I will make knot-A backup for knot-A frequently (parameters: +nozonefile +nojournal +notimers +kaspdb +catalog +noquic), then copy each backup to knot-B and online restore. The error
2023-11-16T09:16:20+0800 error: [top.] zone event 'load' failed (value is out of range)
occasionally appeared in the knot-B log, and there must be a warning in the front of that log.
2023-11-16T09:16:17+0800 warning: [top.] zone file changed with decreased SOA serial
I don't know what caused this, may I ask how I can troubleshoot it