My ipad air 4 keeps buffering or becomes unresponsive on internet yet my ipad air 2 works fine.

Hello and welcome to Apple Support Communities, Fitzyscot!

We understand your iPad Air becomes sluggish or unresponsive when you try streaming something. We'd be happy to provide information to help you address this.

You mentioned that you've already reset the Wi-Fi. Did you mean you reset network settings as described here?

If your iPhone, iPad, or iPod touch won’t connect to a Wi-Fi network

If so, you may want to try restoring to factory settings and testing to see if this continues with a new setup:

How to back up your iPhone, iPad, and iPod touch

Restore your iPhone, iPad, or iPod to factory settings

If after setting up as new, your iPad Air is able to stream correctly, try restoring the backup:

Restore your iPhone, iPad, or iPod touch from a backup

If the issue returns after restoring the backup, set it up as new again. It may be that the issue is located within the software with your current setup.

Let us know the results.

Have a great day!

Thanks for getting back to us, Fitzyscot!

Sounds like there is some interference with your newer iPad Air and your router. If you haven't already tried, restart your router. This may resolve the issue entirely.

However, have a look at the following article since it matches your description of the buffering:

Resolve Wi-Fi and Bluetooth issues caused by wireless interference

If you continue having the issue after following the steps there, please reach out to Apple Support: Contact Apple for support and service

Regards.