Device unable to receive connection after 4 connections

Hello Team,

So I have my custom splash package running on openwrt and it has been working fine. My device can take up to 25 connections at the same time. I realized my devices started behaving strangely a few days ago. I have 8 of my devices serving an audience of 100 people and the audience can hardly connect. I realized one device is taking only just 4 devices and no other device can connect when we try.

Any help will be greatly appreciated.

Device Specs below

16MB Flash
64MB DDR2 Ram
MediaTek MT7628AN CPU
1 x USB 2.0 USB Interfaces
300 Mbps Max Speed
10/100Mbps Wired Tx. Rate
2.4GHz Frequency
1 x10/100Mbps WAN Ports
b/g/n WLAN 2.4GHz
5 VDC, 2.0A Power Supply
8000 mAH Battery
1 (Combined with WAN) Lan Ports
Yes 4G LTE Module
1 x Micro Sim Sim Card
Built in 5dBi Dual Antenna Antenna