Jetpack Sync - Options Table Overload - jetpack_callables_sync_checksum

The option_name jetpack_callables_sync_checksum is adding a row to wp_options every minute with same values.

Running
Multisite
WordPress 4.8.3
Jetpack 5.4

XMLRPC blocked but Automattic IPs whitelisted.

Start by reproducing the repeated writes to the jetpack_callables_sync_checksum option on a multisite WordPress installation, using the reported WordPress and Jetpack versions where possible. Trace what triggers the write and verify that the option no longer adds identical rows every minute while preserving the required sync behavior.

Written by the indexing model from the issue text.