Dear @Soofi,

Im using EAP 110 outdoor x 10 nos and EAP 115 x 4 nos. All eap connected to the POE D-Link Access switch (eap 110 outdoor doesn't work poe switch) also N300 tp-link controller  connected to the same POE. The issue is sometimes its disconnecting and reconnecting automatically. 

What's the firmware version of your EAPs? Are you using Omada software controller or OC200, what's the version?

May I know the application scene and the network topology? How far away is the EAPs away from each other?

EAP110-Outdoor and EAP115 all work on 2.4GHz, you may refer to the FAQ below to avoid wireless interference.

How to optimize wireless performance of EAP products, https://www.tp-link.com/support/faq/2511/

If the EAPs are deployed evenly and the wireless clients are randomly distributed, you may configure Load Balance to avoid a single EAP overloaded with clients, but ensure it's properly configured. Here is a FAQ for your reference. 

How to Configure Load Balance Omada Controller, https://www.tp-link.com/support/faq/2093/

@Fae 

Controller OC200 version 4.2.8.

EAP firmware version 5.0.0.

distance between each EAPs 10 meter.

-> internet -> POE AS -> OC200 -> Access Switch (50 meter cat6) -> EAP's

eg:

EAP......10m......EAP........

 |
20m

@Fae 

We are using 3 SSID, and one of the SSID is hidden. 
 

Sometimes all the SSID disappear and reconnect automatically.