add:
explicit-exit-notify 2
to client udp config
--explicit-exit-notify [n]
In UDP client mode or point-to-point mode, send server/peer an exit notification if tunnel is restarted or OpenVPN process is exited. In client mode, on exit/restart, this option will tell the server to immediately close its client instance object rather than waiting for a timeout. The n parameter (default=1) controls the maximum number of retries that the client will attempt to resend the exit notification message.
