How to solve RRAS (Windows Server 2008 R2) and L2TP Server (Mikrotik) connection problems?

Question

Computer networks

There is a server with Windows Server 2008 R2 and two Mikrotik hAP ac lite in remote offices.
The server is connected to the internet via Huawei HG8245T. All connections are forwarded by the router to the server using DMZ.
L2TP Server is enabled on Mikrotiks. L2TP is used to operate Active Directory over the Internet.
The server in RRAS has 2 persistent connection demand-dial interfaces and 2 static routes for these connections. Office #1 network - 10.0.12.0/24, office #2 - 10.0.13.0/24.

From time to time (2-4 times a day) at the same timethe connection between the server and Mikrotiks disappears (RDP stops working, pings do not go in both directions). At the same time, in RRAS and in Winbox, the connection is displayed as connected. When one connection is reconnected, communication is restored on both .
Disabling all firewall rules and antivirus on the server does not solve the problem.
During normal operation, pings from the server to Mikrotiks and devices behind them pass, everything functions normally.

Answer 1

Throw out the Windows server and install another mikrotik. At one time (about 8 years ago) they applied the proposed solution and ... HELPED !!!