We are also having troubles updating this plugin. We recently did a large upgrade of Jenkins and various plugins. This was the only failed installation due to a checksum mismatch.
Please let me know if you would like additional information or logs
Error below is from the Update Center on Jenkins 2.49
java.io.IOException: Downloaded file /var/lib/jenkins/plugins/windows-slaves.jpi.tmp does not match expected SHA-1, expected 'Ix+nWMcnJcPus+tnvxKhhmunuZA=', actual '2jmj7l5rSw0yVb/vlWAYkK/YBwk='
at hudson.model.UpdateCenter.verifyChecksums(UpdateCenter.java:1811)
at hudson.model.UpdateCenter.access$1100(UpdateCenter.java:148)
at hudson.model.UpdateCenter$InstallationJob.replace(UpdateCenter.java:1962)
at hudson.model.UpdateCenter$UpdateCenterConfiguration.install(UpdateCenter.java:1197)
at hudson.model.UpdateCenter$DownloadJob._run(UpdateCenter.java:1681)
at hudson.model.UpdateCenter$InstallationJob._run(UpdateCenter.java:1876)
at hudson.model.UpdateCenter$DownloadJob.run(UpdateCenter.java:1652)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:473)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at hudson.remoting.AtmostOneThreadExecutor$Worker.run(AtmostOneThreadExecutor.java:110)
at java.lang.Thread.run(Thread.java:745)
Anything in system logs? Are you able to reproduce it in 2.30?