The AQ637X OSA has a feature called Auto Offset that it performs every 10 minutes. What this feature does is zero out the OP amps in the OSA to ensure constant level accuracy. This feature will however, stop the OSA from performing any functions during its operation which includes responding to remote control commands.
One workaround is to turn Auto Offset off when performing testing; however this is not a recommended solution as it may affect the accuracy of your measurement. Another workaround, for automated testing, is to lengthen the timeout so that you wait for a response when the offset procedure is being performed. It takes about 30 seconds to complete the offset calibration on most OSAs.
One additional note is that while the OSA is performing Auto Offset, you will see an indication in the lower leftmost corner of the screen.