Unable to load macro browser after upgrade to 6.6.12

[Scott Metoyer]

We recently upgraded our on-prem instance of Confluence to 6.6.12.

After upgrade the macro browser stopped working (clicking the link menu bar does nothing).

The Chrome console displays this error:

Error requesting macro browser metadata:
[object Object] 

The Confluence log has these errors:

 2019-04-16 06:41:12,257 WARN [http-nio-443-exec-3] [confluence.impl.hibernate.ConfluenceHibernateTransactionManager] doRollback Performing rollback. Transactions:
->[null]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT (Session #377363158)
-- referer: redacted | url: /plugins/macrobrowser/browse-macros.action | traceId: 52a92018ef2e3b04 | userName: redacted 
2019-04-16 06:41:12,267 ERROR [http-nio-443-exec-3] [[Standalone].[localhost].[/].[action]] log Servlet.service() for servlet [action] in context with path [] threw exception [Servlet execution threw an exception] with root cause
java.lang.UnsatisfiedLinkError: sun.misc.VM.latestUserDefinedLoader0()Ljava/lang/ClassLoader;

Cleaning the plugin cache has no effect.

Any idea what the issue is?