SFT1200 Opal : forwarding with external switch

I have 2 Gl-inet routers. These routers are placed behind a main router. The first (AR750 Creta) works perfectly with a Zyxel external switch to which 2 IP cameras are connected. I configured the port forwarding and I have remote access to the cameras. With the second (sft1200 Opal) the port forwarding does not work with the same switch. On the other hand, it works if the cameras are connected via wifi. Could you help me resolve this problem?

Is the switch behind of AR750 and SFT1200, or between them and the main router?

The camera connect via wifi to SFT1200?

What does not work is camera conncect via cable?

Hi Alzhao
Switch is behind sft1200 and port forwarding fail. On switch I connected 2 cameras.
But when I connect the cameras by wifi to sft1200 port forwarding run well.

Main router → Sft1200 → switch cable → 2 cameras : port forwarding fail
Main router → Sft 1200 → wifi → 2 cameras : port forwarding OK
With same configuration :
Main router → AR750 → switch cable → 2 cameras : port forwarding OK

My switch is a Zyxel Switch GS105B
If I connect a camera ip directly with cable on sft1200 then port forwarding is OK
So it seems that Zyxel is disruptive but it run perfectly with AR750.

opkg update; opkg install nmap on your Certa & scan the Opal. See what pops.