To help alleviate some AirPlay problems while using an older MacBook, try the following:
-Quit (not just close) out of any applications that you don't need open.
-Quit out of Chrome, unless you absolutely need it. If you must use Chrome, limit the number of browser tabs that you have open.
-Restart the MacBook, but uncheck the box seen below.
-If you're playing a video, use the handoff feature instead of AirPlay. Handoff is the AirPlay icon within the video window.