They discontinued the audio only Powerline Stereo Audio Station
I had problems with WiFi on 2.4GHz. I found that each of 12 channels is 4 channels wide resulting in only 3 channels. I had constant dropouts. I switched to 5GHz and haven't had a dropout for many years. It has 23 non-overlaping channels, is not very popular and penetrates walls poorly - big advantage because walls shield you from the signals outside of your house. My router is located in similar distance of about 20 feet, but is in the basement, separated by floor. Try playing with settings - like auto channel selection. Check how many 5GHz channels are occupied. Perhaps auto channel picks up channels with higher number (and frequency) that tend to be used by radar, weather stations and military.
900MHz has disadvantage of penetrating walls better and some of the cell phones might still use it, not to mention that common frequency for the networks of Smart Power Meters is 902MHz (and 2.4GHz)
2.4GHz was really bad. I discovered that my microwave has frequency identical (listed on the label) to one of the channels. I had long dropouts when my wife used it.