In my limited nostr understanding this might be connected to the set of relays that you use. Some might go offline temporarily, some go offline forever. All the following events that were stored there and nowhere else are now lost.
Is my logic plausible? nostr:npub1mhcr4j594hsrnen594d7700n2t03n8gdx83zhxzculk6sh9nhwlq7uc226 nostr:npub1794vv7hl7y6q2qw0y7m7h60rpphmvt5h7pzt5sr78z6assj6w0eqagwjhd