Setting an Option-based field, such as a Single-select or multi-select custom field, with a value that contains an ß character fails. The same is true when copying an Option value that contains this character.
This is due to a bug in Jira's com.atlassian.jira.issue.customfields.manager.CachedOptionsManager#findByOptionValue method. Bug is tracked by Atlassian as https://jira.atlassian.com/browse/JRASERVER-66874
If Atlassian is not willing to fix the issue, we should look for a workaround.
JIRA 7.5.3 standalone