We826-t2 4g Connection Goes Down!

Hi, my name is Gabriel, and I am confused about the behavior of WE826-t2 router. . It has a Quectel EC25-AU as Modem.

Model ZBT-WE826 (16M)
Architecture MediaTek MT7620A ver:2 eco:6
Firmware Version GoldenOrb_2020-03-01 ( OpenWrt 18.06.7 )
Kernel Version 4.14.167

After a few hours of using it. 4G connection goes down and the only way to reconnect it is rebooting the router.

Really I don't understand what is happening. In modem appears to be allright.
I took a log and kernel capture:

Wed Aug 26 01:10:16 2020 user.notice ModeChange: 0 7
Wed Aug 26 01:10:24 2020 user.notice ModeChange: 0 7
Wed Aug 26 01:23:58 2020 daemon.notice netifd: wan1 (3333): udhcpc: sending renew to 10.241.242.193
Wed Aug 26 01:26:50 2020 daemon.err uhttpd[1795]: luci: accepted login on / for root from 192.168.1.112
Wed Aug 26 01:38:26 2020 daemon.err uhttpd[1795]: sh: write error: Broken pipe
Wed Aug 26 01:38:26 2020 daemon.err uhttpd[1795]: sh: invalid number ''
Wed Aug 26 01:38:26 2020 daemon.err uhttpd[1795]: sh: invalid number ''
Wed Aug 26 01:39:29 2020 user.notice ModeChange: 0 6
Wed Aug 26 01:40:27 2020 user.notice ModeChange: 0 7
Wed Aug 26 01:41:32 2020 daemon.notice hostapd: wlan0: AP-STA-DISCONNECTED f4:8c:50:f0:ac:f8
Wed Aug 26 01:41:35 2020 daemon.info hostapd: wlan0: STA f4:8c:50:f0:ac:f8 IEEE 802.11: authenticated
Wed Aug 26 01:41:35 2020 daemon.info hostapd: wlan0: STA f4:8c:50:f0:ac:f8 IEEE 802.11: associated (aid 1)
Wed Aug 26 01:41:35 2020 daemon.notice hostapd: wlan0: AP-STA-CONNECTED f4:8c:50:f0:ac:f8
Wed Aug 26 01:41:35 2020 daemon.info hostapd: wlan0: STA f4:8c:50:f0:ac:f8 WPA: pairwise key handshake completed (WPA)
Wed Aug 26 01:41:35 2020 daemon.info hostapd: wlan0: STA f4:8c:50:f0:ac:f8 WPA: group key handshake completed (WPA)

I suppose that it Goes down when:
Wed Aug 26 01:23:58 2020 daemon.notice netifd: wan1 (3333): udhcpc: sending renew to 10.241.242.193

Kernel log:
[54.614097] br-lan: port 2(wlan0) entered disabled state
[ 54.619911] device wlan0 entered promiscuous mode
[ 54.624878] br-lan: port 2(wlan0) entered blocking state
[ 54.630339] br-lan: port 2(wlan0) entered forwarding state
[ 55.178934] br-lan: port 2(wlan0) entered disabled state
[ 56.713670] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
[ 56.720457] br-lan: port 2(wlan0) entered blocking state
[ 56.725885] br-lan: port 2(wlan0) entered forwarding state
[ 72.091840] random: crng init done
[ 72.095331] random: 6 urandom warning(s) missed due to ratelimiting

Please can anyone help me? Thanks.

Gabriel