PPP packets altered from virtual hub

[max_v]

I know this is a strange case, but I use it; I have this case:
I've some clients connected to a MS Vpn server, some of these clients act also as Vpn server (MS incoming connection) so a client connected to the main vpn can connect to the lan of another client; with MS server works.
I try to move the system to SoftEther, using Softether as main server and leave connections from client to client managed by MS incoming connection and MS vpn client, but it doesn't work: clients are connected to Softether server and from a client I can reach other clients with some protocols (ICMP, http, etc.), but if I try to open a PPTP with a MS client doesn't work.
I've analized packets sent by MS client and received by pc that acts as incoming connection server; I found that first packets sent are correct, but the first PPP LCP packet sent arrive changed to destination; in more detail packet is 71 bytes long, first 34 bytes received are the same I sent, remaining are different.

Any idea or workaround?

[thisjun]

SofteEther doesn't change a packet payload usually.
What difference is there?