I'm observing the same error message under 3.2.0 when I have multiple comment blocks in my changeSet.
liquibase.parser.core.ParsedNodeException: Multiple nodes match null/comment
at liquibase.parser.core.ParsedNode.getChild(ParsedNode.java:171)
at liquibase.parser.core.ParsedNode.getChildValue(ParsedNode.java:259)
at liquibase.parser.core.ParsedNode.getChildValue(ParsedNode.java:206)
at liquibase.changelog.ChangeSet.load(ChangeSet.java:250)
at liquibase.changelog.DatabaseChangeLog.createChangeSet(DatabaseChangeLog.java:310)
at liquibase.changelog.DatabaseChangeLog.handleChildNode(DatabaseChangeLog.java:200)
at liquibase.changelog.DatabaseChangeLog.load(DatabaseChangeLog.java:193)
at liquibase.parser.core.xml.AbstractChangeLogParser.parse(AbstractChangeLogParser.java:25)
at liquibase.Liquibase.getDatabaseChangeLog(Liquibase.java:209)
at liquibase.Liquibase.update(Liquibase.java:187)
at liquibase.Liquibase.update(Liquibase.java:174)
at liquibase.integration.commandline.Main.doMigration(Main.java:992)
at liquibase.integration.commandline.Main.run(Main.java:170)
at liquibase.integration.commandline.Main.main(Main.java:89)