Just get Failed - Network error when I try repeatedly to download the latest beta 1.90 version of BoincTasks.
https://efmer.com/boinctasks/download-boinctasks-beta/ (https://efmer.com/boinctasks/download-boinctasks-beta/)
I checked and it download fine, maybe a glitch in the server.
It depends on the browser, some will block this download a couple of times.
You can use the the Update function in BoincTasks Help->Update that doesn't rely on the browser.