when near the periapsis of my orbit , my semi-major axis go down when the kRPC server is running , when down , nothing appen to it

Sorry for the slow response...

If you are still interested in this, could you provide more details? I don't quite follow

No worry,
What i was trying to say is , when mod is installed and server is connected to it, the orbit of the active craft slowly decay like real life, but KSP don't simulate that, shutting down server without doing anything on KSP solve the problem,
I'm not home right now, will provide additional data as picture