There was no couati.err file generated for this date.
You must have had some kind of error.
If you have logging enabled in the GSX Settings, no Couatl.err will be created, but everything will be in the Couatl.LOG file. However, if you restarted the sim, a new Couatl.LOG would have overwritten it, so you must wait for the problem to appear again, and check the Couatl.LOG file instead (assuming you have logging enabled).
Most likely, it was a scenery AFCAD problem, but it's not possible to say for sure without the log file.