This article explains an issue where the arp table is flapping continuously on SRX.

You will notice SRX losing connectivity to all of its directly connected devices. When you monitor the SRX ARP table you will see arp entries flapping the whole time.

This could happen if there is an ARP storm hitting the SRX on any of its interfaces and the default ARP policer gets triggered and starts dropping the ARP packets randomly and silently. This will cause the flap in the ARP cache as well which will eventually lead to communication issues. You need to identify the interface which is receiving the storm and fix the device causing it.