Hello,
Hope you are well. My name is Kristian and I am one of the Engineers from the Small Business support team.
There are many possible causes why you are seeing degraded performance from your WAP551 due to the nature of wireless communications - from configuration (topology, radio settings, wireless settings) to environment issues (signal interference, walls or other objects stopping the signal) and others. My recommendation is to open a support case with us so an Engineer can contact you and help you to resolve your issue in a timely manner. Feel free to open a support ticket from our Support Case Manager or call us so we can open a service request for you.
Kind regards,
Kris