Why does OpenVPN disconnect when using RDP on some networks?

Question

openvpn

Good afternoon, please help with the following problem...
Given:
There is an ASUS RT-AC58U home router (firmware version 3.0.0.4.380_8457, latest) with a white IP, no problems with the Internet.
It has an OpenVPN server with TAP interface, UDP protocol, TLS authorization. Communication between clients is allowed. There are no problems with the VPN itself, the connection is stable. The clients are configured to completely redirect all traffic to the home router, other software and games work stably.
The problem itself:
I connect from a working WiFi (as I was told, there are no blockages, it is completely open) on a laptop, I use OpenVPN, which successfully keeps the connection. But as soon as I try to connect to my home PC, the connection fails. To be precise, the break occurs after the RDP connection is established, it may have time to show a couple of frames before the break, then the tunnel is completely terminated, only reconnection helps (OpenVPN itself shows that the connection is still active).
There are no errors in the OpenVPN logs of the laptop and router. At the same time, from the phone, in the same wfi network, RDP works fine. If you share a wifi network via USB to a laptop, the problem remains, but if you connect via a mobile network, the tunnel does not break, and RDP connects successfully.
There is one caveat: a couple of times I still managed to connect through a working wifi, I could not figure out the pattern.