Something I just noticed.....your client is running an unreleased version of openvpn, 2.5
Latest official release (and what is used for the server) is 2.4.6
OpenVPN levels have been somewhat finicky lately.
I still can't explain why the firmware level is making a difference, but do you have an older client pkg you can try?
Certifcate only connection work fine.
I tested the following OS/openvpn/auth clients against openvpn server on 34E3 using similar client configs.
I disabled vpnclients on the router. Then attempted to connect each client (via LAN).
Android 6.0.1, OpenVPN for Android 0.7.5 (Openvpn 2.5-icsopenvpn)
certificates only: all good.
certificates and user-pass-auth: 1st session OK, subsequent sessions don't get past user auth (according to server log)
Ubuntu 16.04, OpenVPN 2.3.10
certificate only: all good.
certificates and user-pass-auth: same results as with the android client.
In both instances, the failed connections progress as far as:
Code:
AUTH-PAM: BACKGROUND: received command code: 0
AUTH-PAM: BACKGROUND: USER: keeka
Code:
AUTH-PAM: BACKGROUND: my_conv[0] query='Password:' style=1
Wed Sep 12 09:18:00 2018 us=902168 192.168.0.35:48527 PLUGIN_CALL: POST /usr/lib/openvpn-plugin-auth-pam.so/PLUGIN_AUTH_USER_PASS_VERIFY status=0
Wed Sep 12 09:18:00 2018 us=902389 192.168.0.35:48527 TLS: Username/Password authentication succeeded for username 'keeka'
Deliberately entering incorrect credentials on what would otherwise be a successful first connect, results in the same failure in subsequent connection attempts, until you restart the openvpn server.