If the Trigger is not using the Credential the folder would not be able to be monitored at all.
We would never be able to see \\Mf004\fst\Export\ without a Credential. You can try this for yourself by deselecting the Credential - you will not even be able to start monitor without error.
In your case the Credential might not be inherited in the Watcher_changed event or that your user requires some specific permissions.
If this was a general problem we would have received a lot of feedback as a lot of our users are using the File Trigger for watching changes.
It would be interesting to know if this is related to:
1. the user that you use
2. the operative system (local)
3. the remote operative system or particular instance
4. the particular machine
We would really appreciate if you could do the following tests to pinpoint this:
1. from the same VisualCron server monitor another remote folder on another machine
2. If this does not work (same error) - then install VisualCron temporary on another machine and test on instance 1 and 2.