Problem: Frequents disconnect after implementing VLANs over Mikrotik router. ARP in Mikrotik was failing. Most probably due to Shelly WiFi is not strong enough to transmit response to AP.

Infrastructure: Shelly 2.5 over WIFI to Unify AP over LAN to Mikrotik hAp ac2

Shelly settings

I set those because of VPN.

• Static IP set directly in Shelly
• Advanced - Developer Settings -> CoIoT enabled

Solution

Switch off ECO mode on Shelly solved the problem.

Steps below were done first as a part of troubleshooting but issue remained. I have not change the settings back. Leaving those there as those might help your issue.

• UniFi settings
  • Transmit power: Medium
  • 802.11 DTIM Period: 2,4GHz: 1
• Shelly firmware updated to latest beta