When you’re watching movies wirelessly, and it’s buffering, are you on your laptop, or a smart TV, or a Roku - what kind of device are you watching on?
What type of wireless ESS device are you using: is there a wireless router and a separate modem, or an all-in-one modem/router?
How far is it from your laptop to the wireless modem-router?
Are there a lot of walls between your viewing device and the wireless point?