After a routine descriptor refresh, the reserve node was slow to resolve for roughly a day. This is normal Tor behaviour. When a hidden service publishes fresh descriptors, they take time to propagate through the distributed hidden service directory, and during that window some clients find the address before others.
The primary and secondary were unaffected and carried traffic normally. Readers who specifically needed the reserve during that day saw longer resolution times or the occasional failure to connect, both of which cleared as propagation finished.
No action was required. The entry is logged because the explorer records propagation lag as an informational event, so a reader who hit it can see it was expected rather than a problem with the node.