phppb 3.1.9: Error every time a user posts a message

Hello,

I just upgraded my forum to 3.1.9 straight from 3.1.8.
Note that I am using mssql.

Since then, I have this problem every time a user posts a new message:

SQL ERROR [ mssqlnative ]

SQLSTATE: 42000 code: 3988 message: [Microsoft][SQL Server Native Client 11.0][SQL Server]Newtransaction is not allowed because there are other threads running in the session. [3988]

I tracked this problem down to the function get_notification_type_id, which is creating a new transaction. This functionality has been recently added to phpbb 3.1.9 with the following change (as seen in Github's history):

https://github.com/phpbb/phpbb/commit/10004c4032a86364c834574a670032d2676b87cb

I have reverted this file (phpBB/phpbb/notification/manager.php) to the 3.1.8 version for now, the previous version is working fine. Any ideas?

The callstack is:

FILE: [ROOT]/phpbb/notification/manager.php
CALL: phpbb\db\driver\factory->sql_transaction()

FILE: [ROOT]/phpbb/notification/type/base.php
CALL: phpbb\notification\manager->get_notification_type_id()

FILE: [ROOT]/phpbb/notification/manager.php
CALL: phpbb\notification\type\base->set_notification_manager()

FILE: [ROOT]/phpbb/notification/manager.php
CALL: phpbb\notification\manager->load_object()

FILE: [ROOT]/phpbb/notification/type/post.php
CALL: phpbb\notification\manager->get_item_type_class()

FILE: [ROOT]/phpbb/notification/manager.php
CALL: phpbb\notification\type\post->find_users_for_notification()

FILE: [ROOT]/phpbb/notification/manager.php
CALL: phpbb\notification\manager->add_notifications()

FILE: [ROOT]/includes/functions_posting.php
CALL: phpbb\notification\manager->add_notifications()

FILE: [ROOT]/posting.php
CALL: submit_post()

Thanks a lot,