There was a test failure on the tip of develop (i.e., the version in 3.3.11), here: http://build.wiredtiger.com:8080/job/wiredtiger-test-format-stress-sanitizer-ppc/1400/console
That indicates that transaction time went backwards between calls to reconciliation for a tree. This relates to the new btree->include_checkpoint_txn flag, and when it is set.
I believe it’s a false alarm — i.e., the assertion is firing and we need to fix that, but it isn’t telling us that something is fundamentally wrong. Instead, we need to wait to set the flag until after the checkpoint transaction has started.