Found a solution to this problem. I made these changes to my wifi (same device as the router), and it has not happened since (even though Roku 4 is plugged via ethernet):
- Bluetooth Coexistence -> changed from “Enabled” to “Disabled”
- 802.11n Preamble -> changed from “Green Field” to “Mixed Mode”
- WMM -> changed from “Auto” to “Enabled”
** No ACK -> Disable
** APSD Mode -> Enable