Your network is flip-flopping.
Did you change the DHCP server settings recently?
Is the cable clicked tight into the Syno & switch/router ?
Jan 24, 2023 19:00:40.681 [0x70977d44] DEBUG - NetworkInterface: Netlink information message family=0, type=65534, index=6, flags=0x1090, change=0xffffffff
Jan 24, 2023 19:00:40.681 [0x70977d44] DEBUG - Network change.
Jan 24, 2023 19:00:40.681 [0x70977d44] DEBUG - NetworkInterface: Notified of network changed (force=0)
Jan 24, 2023 19:00:40.682 [0x70977d44] DEBUG - Network change notification but nothing changed.
Jan 24, 2023 19:00:40.682 [0x70977d44] DEBUG - NetworkInterface: received Netlink message len=1072, type=RTM_NEWLINK, flags=0x0
Jan 24, 2023 19:00:40.682 [0x70977d44] DEBUG - NetworkInterface: Netlink information message family=0, type=65534, index=6, flags=0x110d1, change=0x1
Jan 24, 2023 19:00:40.682 [0x70977d44] DEBUG - Network change.
Jan 24, 2023 19:00:40.682 [0x70977d44] DEBUG - NetworkInterface: Notified of network changed (force=0)
Jan 24, 2023 19:00:40.682 [0x70977d44] DEBUG - Network change notification but nothing changed.
Jan 24, 2023 19:00:40.682 [0x70977d44] DEBUG - NetworkInterface: received Netlink message len=72, type=RTM_DELADDR, flags=0x0
Jan 24, 2023 19:00:40.682 [0x70977d44] DEBUG - NetworkInterface: Netlink address message family=2, index=6, flags=0x80
Jan 24, 2023 19:00:40.682 [0x70977d44] DEBUG - Network change.
Jan 24, 2023 19:00:40.682 [0x70977d44] DEBUG - NetworkInterface: Notified of network changed (force=0)
Jan 24, 2023 19:00:40.683 [0x70977d44] DEBUG - Network change notification but nothing changed.
Other things I see is a bunch of “Client Disconnected” errors.
( A lot of these )
Jan 24, 2023 19:02:40.360 [0x6eb4ad44] DEBUG - [Req#1d8] Final path: "/volume1/@appstore/PlexMediaServer/Resources/Plug-ins-915986d62/WebClient.bundle/Contents/Resources/js/chunk-975-b967d0765d0ea01caafc-plex-4.87.2.25887-d04a1ad.js"
Jan 24, 2023 19:02:40.360 [0x6eb4ad44] DEBUG - Content-Length of /volume1/@appstore/PlexMediaServer/Resources/Plug-ins-915986d62/WebClient.bundle/Contents/Resources/js/chunk-975-b967d0765d0ea01caafc-plex-4.87.2.25887-d04a1ad.js is 4581 (of total: 4581).
Jan 24, 2023 19:02:40.485 [0x729aed44] DEBUG - Failed to stream media, client probably disconnected after 84680 bytes: 32 - Broken pipe
Jan 24, 2023 19:02:40.485 [0x729aed44] DEBUG - Completed after connection close: [192.168.1.110:57474] 200 GET /web/js/chunk-756-00b43927c5823788c98b-plex-4.87.2.25887-d04a1ad.js (10 live) GZIP 259ms 84680 bytes (pipelined: 7)
Jan 24, 2023 19:02:40.486 [0x729aed44] DEBUG - Failed to stream media, client probably disconnected after 46720 bytes: 32 - Broken pipe
Jan 24, 2023 19:02:40.486 [0x729aed44] DEBUG - Completed after connection close: [192.168.1.110:57485] 200 GET /web/js/chunk-17-05d0896613fac5ce82ec-plex-4.87.2.25887-d04a1ad.js (9 live) GZIP 446ms 46720 bytes (pipelined: 1)
What’s the MTU ? Is it 1500 (default) or did you set something else ?