I had an issue quite a few time that checkout has been broken (interrupted during update, etc.)
To fix it it's sufficient to do 'svn cleanup'. However subversion-plugin doesn't support it.
In case of a broken checkout poll-scm triggers a new build

https://repo/svn/project/trunk is at revision 3,211
  (changed from 3,210)

but SVN doesn't update this repository:

Fetching 'https://repo/svn/project/trunk' at -1 into 'D:\Jenkins\jobs\Project\workspace\project'

When I went to the host and than do 'svn up' it complains :

14:06:28 Fetching external item into 'project':
14:06:28 svn: warning: W155037: Previous operation has not finished; run 'cleanup' if it was interrupted

With mentioned 'cleanup' option it would be possible to avoid such a situation. An additional issue is that subversion-plugin doesn't show information about W155037, so build is trigger but without information that repository hasn't been updated.