Spark 2.7.0_665 Not updating contact list across a subnet

We run Spark 2.7.0_655 with JRE Version 1.7.0_51 across 2 subnets (call them 0 and 1).  Clients are on Win 7 x64.

Openfire 3.9.3 is run on Subnet  0, and all clients work well.  However, a client on subnet 1 will not show up in the contact lists on subnet 0 until they restart the client.  This appears to be unique to this 1 client.

We are not using LDAP.

Any help would be appreciated.

Thanks