Another option if the router can't be repaired is to disable the wifi radio on the router fully and connect up a external 2.4Ghz wifi AP for 2.4Ghz signals. Or even turn off both radios and connect up a newer dual band AP ethernet connected to the router. Can connect up another R9000 in AP mode or find something like a Orbi system or anything to run in AP mode while using the R9000 has the main host router.