I also had the same problem that the password was not changed automatically after changing in FileVault.

For this I had written a small script for the users. Users can change the password manually in Self Service. Maybe it will help someone.


```
#!/bin/sh


##########################################################################
# Shellscript		:	Allows you to change the FileVault password
# Autor				:	Andreas Vogel, 31.10.2019	
##########################################################################


## variables

user=$(stat -f '%u %Su' /dev/console | cut -d ' ' -f 2)
UUID=$(dscl . -read /Users/$user GeneratedUID | awk '{print $2}')

askPassphrase () {
	osascript <<EOF - 2>/dev/null
tell application "SystemUIServer"
	activate
	text returned of (display dialog "$1" default answer "" with hidden answer)
end tell
EOF
}

jamfHelper="/Library/Application Support/JAMF/bin/jamfHelper.app/Contents/MacOS/jamfHelper"
jamf="/usr/local/bin/jamf"


## Icon
FileVaultIcon="/Library/Application Support/JAMF/SmallFileVaultIcon.png"
ErrorIcon="/Library/Application Support/JAMF/France_road_sign_A14.svg.png"
SuccessfulIcon="/Library/Application Support/JAMF/ok-1976099_640.png"

######################################################################################################################################

## Messages
Message="
This program synchronizes the Windows password and the FileVault password.
Only proceed if the Filevault password does not match the current Windows password."

FailedPwMessage="
The verification of the password failed, please re-enter the new password."

FailedPwMessageAgain="
The input does not match again. The program is ended."

FailedChange="
The password could not be changed. Try again. If the problem persists, contact the Mac_IT."

SuccessfulChange="
Your password has been changed successfully."

######################################################################################################################################

## Query whether the user really wants to change the password. 
HELPER=$("$jamfHelper" -windowType utility -icon "$FileVaultIcon" -title "Change FileVault password" -description "$Message" -button1 "OK" -button2 "Cancel" -cancelButton "2" -defaultButton 2)
			echo "Jamf Helper Exit Code: $HELPER"

## If the user agrees, the old password and the new password will be requested. 

if [ "$HELPER" == "0" ]
then
		oldPassphrase=$(askPassphrase 'Please enter the old password.') || exit 						
		newPassphrase=$(askPassphrase 'Please enter the current Windows password.') || exit 
		newPassphrase2=$(askPassphrase 'Please enter the current Windows password again.') || exit	
		
				
## Check whether the new password matches.
		if [[ $newPassphrase != $newPassphrase2 ]]
		then 
				
				HELPER=$("$jamfHelper" -windowType utility -icon "$ErrorIcon" -title "Wrong Entry" -description "$FailedPwMessage" -button1 "OK" -defaultButton 1)
				echo "Exit Code: The entry did not match"
				
				newPassphrase=$(askPassphrase 'Please enter the current Windows password.') || exit 
				newPassphrase2=$(askPassphrase 'Please enter the current Windows password again.') || exit
		fi
		
## Check again. If the recheck is faulty, the tool is terminated. 		
				if [[ $newPassphrase != $newPassphrase2 ]]
				then 
				
					HELPER=$("$jamfHelper" -windowType utility -icon "$ErrorIcon" -title "Renewed wrong entry" -description "$FailedPwMessageAgain" -button1 "OK" -defaultButton 1)
					echo "Exit Code: Die Eingabe war erneut falsch."
				
					exit 1			
				fi
		
## If the tool was not closed, the password is changed. 			
					if diskutil apfs changePassphrase disk1s1 -user $UUID -oldPassphrase $oldPassphrase -newPassphrase $newPassphrase
					then
				
						printf HELPER=$("$jamfHelper" -windowType utility -icon "$SuccessfulIcon" -title "Successful Change" -description "$SuccessfulChange" -button1 "OK" -defaultButton 1)
						echo "Exit Code: Password has been changed succesfully."
					
					else
					
						printf HELPER=$("$jamfHelper" -windowType utility -icon "$ErrorIcon" -title "Error" -description "$FailedChange" -button1 "OK" -defaultButton 1)
						echo "Exit Code: Password could not be changed. Is the old password correct?"
					fi

fi

exit 0
```

https://www.jamf.com/jamf-nation/discussions/30895/mojave-filevault-ad-pw-mismatch-fix