Why does the Internet disappear on the router?

Question

Computer networks

Hello!

On the Mikrotik RB951Ui-2HnD router, the Internet from the Huawei E3372 4G modem disappears on all devices. This happens in a random sequence. The interface itself does not fall off. Internet detection detector shows that the Internet is there, but it is not. The power supply changed to 12V and 2A. Now I use a 19V and 1.58A power supply, but the result is the same. Before that, there was a D-Link dir 825 router and the Internet did not fall off. Tell me, what could be the problem?
Mikrotik firmware 6.46.4 (Stable), standard configuration, based on the site
https://www.radio-spektr.ru/articles/nastroyka-mik... The USB extension cable is not used. Mikrotik is powered through a POE injector, but directly the same.