Openvpn client not using data channel offload

[m4rv1n]

Hi everyone,
I have two installation with pfsense 2.6.0 and openvpn server configured.
Configuration is the same (at least from interface).

From the same windows client, if I do connect to Server1, the client use OpenVPN Data Channel Offload adapter, and connection to vpn is very fast; if I do connect to Server2, the client use OpenVPN TAP-Windows6.

Client config for server1 (the one that use data channel offload adapter)
dev tun
persist-tun
persist-key
cipher AES-128-CBC
auth SHA1
tls-client
providers legacy default
client
resolv-retry infinite
remote dnsnameofserver xxxx udp
lport 0
verify-x509-name "xxxxx" name
auth-user-pass
pkcs12 xxxxx-udp-xxxxx-xxxxx.p12
tls-auth xxxxx-udp-xxxxx-xxxxx-tls.key 1
ns-cert-type server
keepalive 10 300
tun-mtu 9000
redirect-gateway def1
push "redirect-gateway def1"

Client config for Server2 (the one that use old tap6 adapter)
dev tun
persist-tun
persist-key
ncp-ciphers AES-128-GCM:AES-128-CBC
cipher AES-128-CBC
auth SHA1
tls-client
providers legacy default
client
resolv-retry infinite
remote dnsnameofserver xxxx udp
nobind
verify-x509-name "xxxxx" name
auth-user-pass
pkcs12 xxxxx-xxxxx-xxxxx-xxxxx.p12
tls-auth xxxxx-xxxxx-xxxxx-xxxxx-tls.key 1
remote-cert-tls server
explicit-exit-notify

Am I missing something so that also the connection to Server2?
Thanks

EDIT: Two parameters in the configuration file can cause this behaviuor (connection to use the tap6)
"ncp-ciphers" and "data-ciphers AES-128-GCM:AES-128-CBC"
I removed these from configration and the connection is now working with data channel offload