SoftEther Error 13 with HAProxy or SNIProxy

I set up an HAProxy (also tried SNIProxy) on my EdgeRouter, sharing port 443 for internal port forwarding and SoftEther Server on Router.

When I connect to port 443 from another SoftEther Server, I got a Timeout error, my error message was in Simplified Chinese on my Windows box, I googled and found other ppl meet same error, English message like:

Error (Error Code 13):
Time-out occurred during VPN session communication. It is possible the connection from the client to the VPN Server has been disconnected.

In my case, external SE connect to RouterIP:443, HAProxy(SNIProxy) listens on 443 and split SE connections to localhost:24443 which is listened by SoftEther on Router.

Since HAProxy/SNIProxy does not handles UDP packets, I tried to set up an port forwarding for UDP 443, not working.

The only solution is TICK the ‘Disable UDP Acceleration / 禁用 UDP 加速功能功能 / UDP 高速化機能を無効にする’ from:
Manage Virtual Hub -> Manage Cascade Connections -> Edit -> Advanced Settings -> Disable UDP Acceleration

SoftEther Error 13 with HAProxy or SNIProxy by @sskaje: