LAN Clients received IP from OpenVPN Remote Access Server

[zsx]

Hi,
I am using a SG-1100.
SG-1100 LAN IP: 10.0.0.1
OpenVPN Remote Access Server IPv4 Tunnel Network: 10.0.1.0/24

This set up ran for months without problem. Then one day, some of the clients on LAN which was supposed to have addresses of 10.0.0.0/24 started getting IP addresses of 10.0.1.0/24. Please advise. Thank you.