From Element:

@MetRonnie:
Trying to sort out MacOS functional test failures, one suspicious thing I'm seeing in the workflow logs is that all cylc messages seem to take almost exactly 10s since the last message (so all task state changes for example seem to take 10s). Don't know what to do with this information however! It is using ZMQ for comms.

(This 10s performance issue is what is causing some tests to fail consistently as the timings just do not allow stuff to run to completion before automatically timing out etc.)

@oliver-sanders:
The default comms timeout is 5 seconds which may be related. Fixing flaky Mac OS tests is fairly low priority.

If we are not too concerned, I'm opening a PR to skip the 2 failing tests on MacOS on GH Actions as there is no point running them if they're going to fail 100% of the time