SRX routing to a next hop outside of interface range!

(Moved this message to SRX forum as it sounds more appropriate)

Hello community!
I’m currently trying to configure a backup Internet to my SRX240 and I have a Huawei 4G router for this purpose (this is the model coming from the ISP).
Now I ordered a static IP, let’s say 80.81.82.83/24. I tried to configure statically but this didn’t work (cannot ping anything on the Internet), so I tried with DHCP and I receive a strange default route: 192.168.8.1.

Here is the setup:
LAN PC            ge-0/0/1.0        SRX       ge-0/0/2.0     4G router (bridge mode)
----------- 192.168.0.10 ---- 192.168.0.1/24   ----------- 80.81.82.83/24-----------


Here is my configuration:
srx>show configuration interfaces ge-0/0/2.0
description Backup-4G;
family inet {
    dhcp;
}

And the result for show interfaces terse:
ge-0/0/2.0              up    up   inet     80.81.82.83/24

srx>show route

inet.0: 9 destinations, 9 routes (9 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

0.0.0.0/0          *[Access-internal/12] 00:10:16
                    > to 192.168.8.1 via ge-0/0/2.0
(…)

Now when trying to send traffic, the device refuses:
srx > ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8): 56 data bytes
ping: sendto: No route to host
ping: sendto: No route to host
ping: sendto: No route to host
^C
--- 8.8.8.8 ping statistics ---
3 packets transmitted, 0 packets received, 100% packet loss

Using traceoptions I can see the following in the logs:
Mar 25 20:43:17 20:43:17.815743:CID-0:RToing DESTINATION addr route-lookup

Mar 25 20:43:17 20:43:17.815743:CID-0:RT:flow_rt_lkup in VR-id: 0

Mar 25 20:43:17 20:43:17.815743:CID-0:RT:flow_rt_lkup: Found route entry 0x5199e210,nh id 0x24, out if 0x0

Mar 25 20:43:17 20:43:17.815843:CID-0:RT:flow_rt_lkup: Route NH points to reject NH type

Mar 25 20:43:17 20:43:17.815843:CID-0:RT:Route-lookup for 8.8.8.8 yielded reject NH

Mar 25 20:43:17 20:43:17.815868:CID-0:RT:  packet dropped, no route to dest


Same result when trying from a computer connected to the SRX.
However when connecting the 4G router to a Windows computer, same routing but it works!
Netstat –rn
          0.0.0.0          0.0.0.0      192.168.8.1    80.81.82.83    25

Anyone has an idea how to resolve this issue? Thanks a lot!