There is a variété of scenarios, all them related with the tool_customlang plugin that have started to fail recently (310_STABLE and up). It's specially noticeable with MSSQL / Oracle databases and/or when the worker is busy / slow.
All them come from the new export () and import () language strings features.
The error seems to be that the "load lang" intermediate step that happens in some of those scenarios takes too long and selenium/behat timeouts.
It affects a number of scenarios (sometimes only 1 fails, other they are 9...).
- (9 failures) : https://ci.moodle.org/job/W.03.04%20-%20Behat%20-%20Chrome%20+%20MSSQL/738/
- (4 failures) : https://ci.moodle.org/job/W.03.04%20-%20Behat%20-%20Chrome%20+%20MSSQL/733/
And the output for the failure (apart from the scenario information that is varying):