I have the same problem with my RUT955 and firmware RUT9XX_R806.08.3.
Openvpn client is configured from a .ovpn file (and also with this configuration you can't see the IP adress, Mask and Time values in the satus-network-openvpn page).
Here is the config file settings :
remote xxx.xxx.xxx.xxx 20000
Any solutions to keep openvpn client connected even after a mobile momentary loose of signal ?