I'm having the same issue. Did you ever resolve your issue?
I'm attempting to do something very similar and have been unable to get this method to work.
Can you enable the Attribute Assistant log file, it will help us troubleshoot the issue.
Edit Log Started at: 10/12/2017 8:41:17 AM
-----------------------------------------
Attribute Assistant start editing
Process Count: 0
Unwiring the events
#######################################################
Inspection - ON_CHANGE
Starting AA
***********************************************************
############ 10/12/2017 8:41:37 AM ################
Setting sort order: Field - RUNORDER
 Querying table for Last Value for layer: Inspection
 Query Used: (TABLENAME = '*' OR TABLENAME = 'Inspection' OR TABLENAME like 'Inspection|*' OR TABLENAME like 'Inspection|%') AND VALUEMETHOD = 'Last_Value'
 Number of results: 0
 Querying table for rules for layer: Inspection
 Query Used: (TABLENAME = '*' OR TABLENAME = 'Inspection' OR TABLENAME like 'Inspection|*' OR TABLENAME like 'Inspection|%') AND ON_CHANGE = 1
 Number of results: 1
 Looping through the rows
 ------------------------------------------------
 Row Info
 Row Number 1
 TableName: Inspection
 FieldName: DATE
 ValueInfo: BMP|LAST_INSPECTED|BMP_ID|BMP_ID
 ValueMethod: UPDATE_LINKED_RECORD
 On Create: 1
 On Change: 1
Checking for Subtype Restriction
 Field Name: DATE was found at index: 2
 Trying: UPDATE_LINKED_RECORD
 Getting Value Info
 Checking values
 Checking Field in Edited Layer
 Checking for related record
 Trying to Copy Value to the Record
 ERROR: Could not Copy: 10/13/2017 12:00:00 AM to field: LAST_INSPECTED
 Related record not found.
 Finished: UPDATE_LINKED_RECORD
 ------------------------------------------------
DONE
---------------------------------------
#######################################################
Wiring the events
Attribute Assistant start editing
Attribute Assistant is being suspended
Attribute Assistant is being turn off
Attribute Assistant is being turn off
**************************************
Closing Log File 10/12/2017 8:41:54 AM
Edit: DATE and LAST_INSPECTED are both date fields. I'm using a file geodatabase.
Looks like a bug trying to copy a date value. Any chance you could send me a sample set of data so I can create a repo case?
Absolutely. I have only been testing a few things so I could send a copy of the entire geodatabase if you'd like. What is the best way to send the file?
email is good, will try to look today - mmiller@esri.com
Justin, what version of the tools are you using? Your data worked fine for me. I changed the date of a record in the inspection table and that value was set in the parent BMP.
I am on ArcMap 10.4.1 and the Add-In Manager tells me that my Attribute Assistant version is 6.26.2015.