Strange corruption RT-AC68U + Huawei e392u

[miogatto]

FIRMWARE: RT-AC68U_378.52_2 Merlin (but problem happens also with previous firmwares)
MODEM: 4G Huawei e392u connected to the usb2/usb3 port (doesn't matter which one)
Modem choice: as default/automatic.
Two interfaces selected USB+WAN (not used) but problem happens also with single USB interface

Problem:
Apparently everything works ok, great throughput. BUT...
when watching streaming videos or webcams, very often stream
stops and needs to be restarted.
When browsing websites, sometimes images are corrupt/broken,
and sometimes webpages aren't loaded fully.

Solution:
just changing router to another router (a Telewell TW-Wlan LTE/4G/3G)
and keeping cables as they are
and using the same e-392u USB-MODEM
the problem is totally solved.

Question:
How is possible that an expensive router fails this way? what should I check?
Thanks for answering

 

[vaszago]

I also own the E392 and runs really well. No problems with streams.
The only problen is the dial up again after the ISP disconnects the internet.
i have solved the problem with a script.