If you have a USB 3.0 device near the router, it can cause interference on Bluetooth as well as the router's 2.4 bands, but the 5.0 will be fine. I was about to give up after using 2 different C9...

If you have an Android phone, download WiFi Analyzer from the Playstore. Check out which channels are being used locally and pick something in the clear.

Download WiFi analyzer for your Android phone from Google Playstore. Take a look at what frequencies are being used in your neighborhood. Choose something away from all the traffic. Try a plain...

Formatting the drive with one of the FAT choices will probably give you speedier reads and writes than NTFS.