Last week the subversion tagging plugin stopped working, and I have so far not been able to pinpoint the source of this error.
This bug is a showstopper for us since the tags are used in other jobs.

The job module have Subversion SCM set up with the following repo:
https://svn.myserver.com/svn/repo/folder1.sub/trunk
The svn-tag plugin is configured with:
https://svn.myserver.com/svn/repo/folder1.sub/tags/${env['BUILD_VERSION']}

The error message from the plugin shows that apparently it tries to copy from an invalid source path.
(note: I have obfuscated url names, but otherwise the number of parts are the same)

Remote Module Location: https://svn.myserver.com/svn/repo/folder1.sub/trunk@2254.
Tag Base URL: https://svn.myserver.com/svn/repo/folder1.sub/tags/0.0.3.2254.
There was no old tag at https://svn.myserver.com/svn/repo/folder1.sub/tags/0.0.3.2254.
Subversion copy failed. svn: File not found: revision 2254, path '/folder1.sub/trunk/folder1.sub/trunk'
svn: '/svn/repo/!svn/bc/2254/folder1.sub/trunk' path not found: 404 Not Found (https://svn.myserver.com)
Build step 'Perform Subversion tagging on successful build' marked build as failure