Error message when checking for updates

After updating to 3.0.15 it is no longer possible to check for updates from within Sourcetree. A message box with the following text appears:

Invalid release entry: 7C20078B2B045E2C881187E39009FD85284F4E83 SourceTree-3.0.15-full.nupkg 23991659

This issue has been reported to the community forum several times but has not been fixed yet. The Atlassian service engineer that responded in https://community.atlassian.com/t5/Sourcetree-questions/Error-sourcetree/qaq-p/971254 does not seem to understand the problem I'm afraid - the latest version that can be downloaded from sourcetreeapp.com is still only 3.0.12, even though 3.0.15 has been released.