Function Send Custom E-mail fails

We had updated our ScriptRunner version from 5.6.6.1-jira8 to 5.6.8.1-jira8 on last saturday. Today i noted that every workflow that had a post function 'Send Custom Email' have not sent the e-mail when it will have to. It shows this error message:

"Script failure, check logs: Cannot deserialize instance of `java.util.ArrayList` out of VALUE_STRING token at [Source: UNKNOWN; line: -1, column: -1] (through reference chain: com.onresolve.scriptrunner.canned.jira.workflow.postfunctions.SendCustomEmailCommand["events"])" and i cannot edit the post function.