I got similar issue that see "Unhandled exception in router" sometimes, and I sovled it by adding error handler for 404.

It was due to nessus scan which sending bad request - authority/path is null, path not start with "/", refer this: https://github.com/vert-x3/vertx-web/blob/master/vertx-web/src/main/java/io/vertx/ext/web/impl/RoutingContextImpl.java#L80-L87