Looking at deploy/undeploy/upload methods in ManagerServlet, HtmlManagerServlet The methods call "if (!isServiced(name))" and if the web application is being serviced (e.g. by another command running in parallel) the methods skip their work and report success. Instead of that they should report that they skipped their work.
This has been fixed in 8.0.x for 8.0.5 onwards and in 7.0.x for 7.0.53 onwards.