Unexpected DeliveryMode.summary_digests causes shunted mail

We're getting the following errors in the logs (mailman 3.0.0, python34-3.4.3-2.el7.centos.x86_64):

Aug 19 13:58:03 2015 (20458) Uncaught runner exception: Digest member "user@example.com" unexpected delivery mode: DeliveryMode.summary_digests Aug 19 13:58:03 2015 (20458) Traceback (most recent call last): File "/usr/lib/python3.4/site-packages/mailman/core/runner.py", line 165, in _one_iteration self._process_one_file(msg, msgdata) File "/usr/lib/python3.4/site-packages/mailman/core/runner.py", line 258, in _process_one_file keepqueued = self._dispose(mlist, msg, msgdata) File "/usr/lib/python3.4/site-packages/mailman/runners/digest.py", line 366, in _dispose email_address, member.delivery_mode)) AssertionError: Digest member "user@example.com" unexpected delivery mode: DeliveryMode.summary_digests Aug 19 13:58:03 2015 (20458) SHUNTING: 1439992683.768731+d0f78197881a171397014742140030e539a9e555

The shunted data shows a a mailman.email.message with digest_path (digest-NN.mmdf file). I don't see the user's email in there, so I think it might try and send to everybody when/if I unshunt it.

The same 3 or 4 emails keep showing up, but interestingly they don't all show up at the same time (emails sanitized such that you can still tell the users apart):

Aug 19 06:06:22 2015 (13582) Uncaught runner exception: Digest member "userA@example.com" unexpected delivery mode: DeliveryMode.summary_digests Aug 19 07:32:55 2015 (20458) Uncaught runner exception: Digest member "userB@example.com" unexpected delivery mode: DeliveryMode.summary_digests Aug 19 07:57:21 2015 (20458) Uncaught runner exception: Digest member "userA@example.com" unexpected delivery mode: DeliveryMode.summary_digests Aug 19 12:06:25 2015 (20458) Uncaught runner exception: Digest member "userB@example.com" unexpected delivery mode: DeliveryMode.summary_digests Aug 19 13:44:18 2015 (20458) Uncaught runner exception: Digest member "userC@example.com" unexpected delivery mode: DeliveryMode.summary_digests Aug 19 13:58:03 2015 (20458) Uncaught runner exception: Digest member "userB@example.com" unexpected delivery mode: DeliveryMode.summary_digests