I recently ran into this issue in WebRTC, which is also easily reproducible in Chromium by rolling to an older lss revision:

$ roll-dep-svn third_party/lss 348bdf8d32b37c8fb2627df7a0a977d1d640e1fc
Pinning src/third_party/lss
to revision 348bdf8d32b37c8fb2627df7a0a977d1d640e1fc
in ./DEPS

$ git diff DEPS
diff --git a/DEPS b/DEPS
index c36d4dae62be..213269dea509 100644
--- a/DEPS
+++ b/DEPS
@@ -84,7 +84,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling lss
   # and whatever else without interference from each other.
-  'lss_revision': '63f24c8221a229f677d26ebe8f3d1528a9d787ac',
+  'lss_revision': '348bdf8d32b37c8fb2627df7a0a977d1d640e1fc'348bdf8d32b37c8fb2627df7a0a977d1d640e1fc7df7a0a977d1d640e1fc',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling NaCl
   # and whatever else without interference from each other.


The resulting change is invalid and makes autorolling fail for this dependency.
The easiest workaround is to modify DEPS to avoid having the same deps multiple times. I think this only affects such deps that share a common variable for the revision.