This article explains the causes for core dump of the flowd daemon on the secondary node after performing ISSU upgrade in chassis cluster

In the issue state, the following flowd core files are generated on the SRX device:

-rw-rw----  1 nobody wheel 525070344 Oct 5  23:06 /var/tmp/flowd_xlr-SPC0_PIC0.core.0.gz
-rw-rw----  1 nobody wheel 534385979 Jan 9  23:41 /var/tmp/flowd_xlr-SPC0_PIC0.core.1.gz
-rw-rw----  1 nobody wheel  71958528 Mar 7  23:15 /var/tmp/flowd_xlr-SPC0_PIC0.core.2.gz

This is a known issue caused by a loss of synchronization or delayed response between the RE and the PFE. The generated core files are non-impacting and do not affect system functionality.

A permanent fix for this issue is included in version 21.4R3-S12.