I have a new python unit test that is failing when using timestamps in checkpoints. I have attached the test, but here's an outline of what it does (similar to test_timestamp02.py):

write 100 k/v into a table. (commit_timestamp == key iterator)
set oldest timestamp to 100
update the 100 k/v with value2 (commit timestamp == 101-200)
session->checkpoint("read_timestamp=100")
make a backup of database directory
open backup database
walk all k/v pairs making sure value2 does not exist

It is failing because there is a single key with value2 in the checkpoint. It is always the last key that was updated before the checkpoint.