How can I force Liquibase to recalculate checksums without re-running the statements?

We're using Liquibase 3.2 with Java 6. Is there a way I can force Liquibase to recalculate checksums without re-running the same statements from our Liquibase files? In our database, I run this ...

update DATABASECHANGELOG set md5sum = null where 1;

However, when I run my Liquibase change scripts, certain executions still fail with the following errors ...

invoking liquibase change script with file /tmp/deploywork/db.changelog-master.xml
running /usr/java/liquibase/liquibase  --logLevel=info --driver=com.mysql.jdbc.Driver --classpath=/usr/java/jboss/modules/com/mysql/main/mysql-connector-java-5.1.22-bin.jar --changeLogFile=/tmp/deploywork/db.changelog-master.xml --url="jdbc:mysql://myservername:3306/my_db" --username=username --password=password update 
INFO 5/13/15 2:15 PM: liquibase: Successfully acquired change log lock
INFO 5/13/15 2:15 PM: liquibase: Reading from my_db.DATABASECHANGELOG
INFO 5/13/15 2:15 PM: liquibase: Successfully released change log lock
Unexpected error running Liquibase: Validation Failed:
     3 change sets check sum
          db.changelog-1.0.xml::1357593229391-25::rob (generated) is now: 7:5cfe9ecd779a71b6287ef2360a6979bf
          db.changelog-7.0.xml::create-address-email-index::davea is now: 7:da0132e30ebd6a1bc52d9a39bb8c56d7
          db.changelog-7.0.xml::add-myproject-event-object-id-col::davea is now: 7:2eab5d784647ce33ef3488aa8c383443


SEVERE 5/13/15 2:15 PM: liquibase: Validation Failed:
     3 change sets check sum
          db.changelog-1.0.xml::1357593229391-25::rob (generated) is now: 7:5cfe9ecd779a71b6287ef2360a6979bf
          db.changelog-7.0.xml::create-address-email-index::davea is now: 7:da0132e30ebd6a1bc52d9a39bb8c56d7
          db.changelog-7.0.xml::add-myproject-event-object-id-col::davea is now: 7:2eab5d784647ce33ef3488aa8c383443

liquibase.exception.ValidationFailedException: Validation Failed:
     3 change sets check sum
          db.changelog-1.0.xml::1357593229391-25::rob (generated) is now: 7:5cfe9ecd779a71b6287ef2360a6979bf
          db.changelog-7.0.xml::create-address-email-index::davea is now: 7:da0132e30ebd6a1bc52d9a39bb8c56d7
          db.changelog-7.0.xml::add-myproject-event-object-id-col::davea is now: 7:2eab5d784647ce33ef3488aa8c383443

    at liquibase.changelog.DatabaseChangeLog.validate(DatabaseChangeLog.java:181)
    at liquibase.Liquibase.update(Liquibase.java:191)
    at liquibase.Liquibase.update(Liquibase.java:174)
    at liquibase.integration.commandline.Main.doMigration(Main.java:997)
    at liquibase.integration.commandline.Main.run(Main.java:170)
    at liquibase.integration.commandline.Main.main(Main.java:89)

Here is one of the change sets that the script is complaining about …

    <changeSet author="davea" id="add-myproject-event-object-id-col">
        <addColumn tableName="sb_myproject_event">
            <column name="OBJECT_ID" type="VARCHAR(32)"/>
        </addColumn>
        <createIndex indexName="SB_myproject_EVENT_IDX"
            tableName="sb_myproject_event"
            unique="false">
            <column name="OBJECT_ID" type="varchar(32)" />
        </createIndex>
        <sql>update sb_myproject_event set object_id=LEFT(SUBSTRING_INDEX(event_data, '&quot;id&quot;:&quot;', -2), 24) where object_id is null and event_data is not null;</sql>
        <!--  Delete older events that no longer need to be processed -->
        <sql>delete from sb_myproject_event where id not in (select q.* from (select e.id FROM sb_myproject_event e, (select object_id, max(date_processed) d from sb_myproject_event group by object_id) o where e.object_id = o.object_id and e.date_processed = o.d) q);</sql>
    </changeSet>

As I said, I only want to recalculate checksums (have to do this because we're changing Liquibase versions).

Rather than clearing the checksums yourself using SQL, it will probably be better to let Liquibase do that by using the clearCheckSums command:

https://docs.liquibase.com/commands/community/clearchecksums.html

Removes current checksums from database. On next run checksums will be recomputed.

Use the command below if you are using maven:

mvn liquibase:clearCheckSums