Having a external with a specific revision causes the system to continuous rebuild.

For example, we have a dependency called "dep" at revision setted at revision 1022.
The structure is:

trunk/externals
trunk/externals/dep
trunk/src

SVN Polls logs are:

Received SCM poll call on for PROJECT on DATE
svn://host/project/trunk is on revision 602
svn://host/dep is on revision 1.022
(changed by 1.008)
Done. Took 87 Ms
Changes found

and the project continuous rebuilds although no changes made.

If we upgrade "dep" revision to latest (1024), now:

Received SCM poll call on for PROJECT on DATE
svn://host/project/trunk is on revision 602
svn://host/dep is on revision 1.024
Done. Took 80 Ms
No changes}

in which one, the builds works as expected