eclipse/jetty.project — comment on commit f8cd2e9a0c8a62cb6ed2d9202560725385f16a97
File: jetty-http-spi/src/main/java/org/eclipse/jetty/http/spi/HttpSpiContextHandler.java line 130
By gregw:

Will check. The difference is that sendError resets the content, so perhaps retry is allowing the authenticator to send content in the response?