How to solve the problem with tcp connection established on mikrotik?

Question

VPN

Everything worked great! Theoretically, there were no changes on mikrotik (VPN server). There were no 100% changes on the VPN client. But on Mikrotik, the message tcp connection established from *.*.*.* appears in the log every second. Empirically revealed that it is the same client who is knocking, he cannot raise a pptp session.
In the debug log:
TCP connection established from *.*.*.*
<123>: LCP lowerdown
<123>: LCP down event in initial state
<234>: rcvd LCP EchoReq id=0xd3
....
But once every Day he nevertheless lifts session. At 6 am, sometimes at 4, for a short period of time. Then it falls off again. Reboot Mikrotik or the client does not help. Other clients work as before without failures.

Answer 1

The "problem", if you can call it that, is solved. The pptp client was a pole camera + TL-MR3220 (with OpenWRT) + Megaphone whistle E3372h in HiLink.
At one fine moment, the camera reached its limit of 30 GB per month, the traffic stopped going, but the megaphone not only cuts off the Internet, but, as I understand it, reduces the speed to the minimum, so HELLO packets come, but not enough for more.
A new month began, we added traffic to the account, and everything worked fine.