Port forwarding dosen't seems to be working on my router.

Quick disclaiment: I have double NAT setup but I dont think that this is the issue, more on that below.

So, here's my setup. I have my ISP modem alongside my TP-Link Router with DMZ and port forwarding configured on both, from my modem to the router and from the router to my NAS. The modem DHCP is configured to use 192.168.2.1 up until 192.168.2.254 while having the TP-Link bound to 192.168.2.2 (both as Fixed IP on the Router and as DHCP Binding on the Modem). The router DHCP is configured to use 192.168.1.0 up until 192.168.1.254 with a fixed ip for my NAS. I'm testing with some random private port 50123 so to exclude the possbility that my ISP is blocking it.

Rigth. When I try to telnet into that port from my phone using 5G (from the internet) all I got is timeout after a while. When I try to do the same but connected to the modem subnet it also timeout after a while. To eliminate the possibility that perhaps my NAS isn't repsponding I tested both accessing the port from within the route subnet (it worked) and from the internet with the NAS connected directly to the modem with the DMZ pointing to it (it also worked). That's why I don't think the issue would be double NAT, becouse if it were the case it would've worked from my phone contected to the modem subnet (as it would not be a double NAT setup in this case). Of course this does not exclude that a double NAT is ALSO a problem, but for sure isn't the only one.

Also a simple ping test from the modem to the external ip of the router show that it's responding properly

PING 192.168.2.2 (192.168.2.2): 56 data bytes
Reply from 192.168.2.2: bytes=56 ttl=64 time=0.9ms seq=0
Reply from 192.168.2.2: bytes=56 ttl=64 time=0.8ms seq=1
Reply from 192.168.2.2: bytes=56 ttl=64 time=0.8ms seq=2
Reply from 192.168.2.2: bytes=56 ttl=64 time=0.8ms seq=3

--- 192.168.2.2 ping statistics ---
4 packets transmitted, 4 packets received, 0% packet loss
round-trip min/avg/max = 0.8/0.8/0.9 ms

What could be messing up this seput?

Before anyone says anything, I know exposing my NAS to the internet with DMZ is usually not a good idea, I'm just using it while trying to make it work, I intend to use only port forwarding for the ports I want to expose then.