Was having an issue with some old Polycom phones not wanting to pull down a new contact list from the server. Quick fix that I found was updating volatile memory settings to from zero to one.

From the Polycom SIP 2.0 Administrator’s Guide

If set to 1, use volatile storage for phone-resident copy of the directory to allow for larger size.

Keep in mind that all of these settings are wrapped in XML. Don’t remove any of that formatting, just change these values in the XML.

Before they were changed in sip.cfg

dir.local.volatile.2meg="0"
dir.local.volatile.4meg="0"
dir.local.volatile.8meg="0"

After they were changed in sip.cfg

dir.local.volatile.2meg="1"
dir.local.volatile.4meg="1"
dir.local.volatile.8meg="1"