Modify Client TLS extension and Expect Handshake Successful

[PseudoPort]

I use valid domain cert and valid CA. I have a proxy that modified TLS extension from ClientHello that added extension holding a dynamic value.
The problem is ServerHello is invalid resulting handshake fail.

Here is the error:
Client TLS handshake failed. The client may not trust the proxy's certificate for mydomain.com (OpenSSL
Error([('SSL routines', 'ssl3_get_record', 'decryption failed or bad record mac')]))

Is there a way that i can rebuild the serverhello with valid sni and cert? Or return ServerHello handshake always return valid?