Wi-Fi signals interference

Wi-Fi congestion is a very complex issue where it is not only a matter of neighbouring wifi networks but also other devices like bluetooth, microwave etc. Bluetooth shares the 2.4 GHz ISM band with other household devices such as cordless telephones, wireless networks, baby monitors, and microwave ovens.
Initial video and or audio transmission delays may occur because of error correction but if it persists you may have wifi interference. Airplay 2 users on a wifi network may read this article on macworld for help.
If you have a strong signal but bad response times then you may have wifi interference or conflicting wifi neighbouring channels and need to change the wifi channel on your router or access point. You may opt to use Auto Wireless Channel, if this is supported by your router configuration, and perform a reboot of your router to determine the free channels.

Read also my recommendations where to put your wifi access point.

Read information concerning cyber security.