Oct 3 16:00:05 ubnt kernel: ESW: Link Status Changed - Port3 Link UP Oct 3 16:00:05 ubnt kernel: ESW: Link Status Changed - Port3 Link Down Oct 3 16:00:07 ubnt kernel: ESW: Link Status Changed - Port3 Link UP Oct 3 16:00:20 ubnt kernel: ESW: Link Status Changed - Port3 Link Down Oct 3 16:00:22 ubnt kernel: ESW: Link Status Changed - Port3 Link UP Oct 3 16:00:22 ubnt kernel: ESW: Link Status Changed - Port3 Link Down Oct 3 16:00:23 ubnt kernel: ESW: Link Status Changed - Port3 Link UP Oct 3 16:00:25 ubnt kernel: ESW: Link Status Changed - Port3 Link Down Oct 3 16:00:42 ubnt kernel: ESW: Link Status Changed - Port3 Link UP Oct 3 16:00:42 ubnt kernel: ESW: Link Status Changed - Port3 Link Down Oct 3 16:00:43 ubnt kernel: ESW: Link Status Changed - Port3 Link UP Oct 3 16:00:47 ubnt kernel: ESW: Link Status Changed - Port3 Link Down Oct 3 16:00:56 ubnt kernel: ESW: Link Status Changed - Port3 Link UP Oct 3 16:00:56 ubnt kernel: ESW: Link Status Changed - Port3 Link Down Oct 3 16:00:58 ubnt kernel: ESW: Link Status Changed - Port3 Link UP Oct 3 16:01:01 ubnt kernel: ESW: Link Status Changed - Port3 Link Down Oct 3 16:10:11 ubnt kernel: ESW: Link Status Changed - Port3 Link UP Oct 3 16:10:11 ubnt kernel: ESW: Link Status Changed - Port3 Link Down Oct 3 16:10:14 ubnt kernel: ESW: Link Status Changed - Port3 Link UP Oct 3 16:10:17 ubnt kernel: ESW: Link Status Changed - Port3 Link Down Oct 3 16:25:19 ubnt kernel: ESW: Link Status Changed - Port3 Link UP Oct 3 16:25:19 ubnt kernel: ESW: Link Status Changed - Port3 Link Down Oct 3 16:25:20 ubnt kernel: ESW: Link Status Changed - Port3 Link UP Oct 3 16:25:22 ubnt kernel: ESW: Link Status Changed - Port3 Link Down Oct 3 16:42:29 ubnt kernel: ESW: Link Status Changed - Port3 Link UP Oct 3 16:42:29 ubnt kernel: ESW: Link Status Changed - Port3 Link Down Oct 3 16:42:31 ubnt kernel: ESW: Link Status Changed - Port3 Link UP Oct 3 16:42:33 ubnt kernel: ESW: Link Status Changed - Port3 Link Down Oct 3 16:42:50 ubnt kernel: ESW: Link Status Changed - Port3 Link UP Oct 3 16:42:50 ubnt kernel: ESW: Link Status Changed - Port3 Link Down Oct 3 16:42:51 ubnt kernel: ESW: Link Status Changed - Port3 Link UP Oct 3 16:42:53 ubnt kernel: ESW: Link Status Changed - Port3 Link Down Oct 3 16:48:08 ubnt kernel: ESW: Link Status Changed - Port3 Link UP Oct 3 16:48:08 ubnt kernel: ESW: Link Status Changed - Port3 Link Down Oct 3 16:48:09 ubnt kernel: ESW: Link Status Changed - Port3 Link UP
Seems like an issue that happens also on PCs when both Wired and WiFi are active and Network Cards obtain IP and DNS address automatically. I don't know how to adjust or reset all network settings on Android
Try disabling WiFi Network from Advanced Network Settings and check again.
To turn off the built-in wireless LAN
Press the HOME button, then select [Settings] > [Network] > [Advanced settings] > [Built-in Wi-Fi] > [Off].