jenkins throws :
ERROR: Failed to update https://XXXXXXX
org.tmatesoft.svn.core.SVNException: svn: E175002: REPORT of '/svn/playspan/!svn/vcc/default': 500 Internal Server Error

on attempt to run build.
on svn server side in the error log:
" Could not access revision times. 500, #0"

I think what happened was:
when build is requested, svnkit is trying to run svn log on the svn server by runnint it between two time stamps - previous build and current time. sometimes either dates were not recorded on svn server or the current dated obtained on the jenkins server is running ahead of svn server and, I think, this causes the problem.
my suggestion:
do not use timestamp at all
instead run log (or svn diff) between two revision numbers, which are always present on svn server.
2. I think running svn log on remote svn server is not very efficient.
I think, would be better:
1. when build is requested, capture current revision on the working space.
2. run svn update
3. capture the revision
4. run log or diff locally between two revisions.

this way, jenkins will communicate to svn server just once instead of multiple times.