I upgraded to the Express 3920 this past March for my living room. I had noticed it was heating up recently. Yesterday, it refused to recognize any wifi signals. Usually mine as well as some nearby signals pop up. Tried unplugging device and rebooting wifi, nothing. All other Roku devices/tv, computer and iPhone can find my wifi but not this one and it recognized the signal just a few days prior, when I last had the tv on in that room.
In order to troubleshoot properly for you, going to need to provide more detailed information about your Roku devices and the steps you are taking and have taken. Still unclear as to whether you are providing power from the wall or the TV and now what this second older Roku device is.
Sounds like you have two Roku devices and two televisions. This will provide a better scenario for testing as you can move them around. Provide all your Roku model numbers and information how you are powering them. With this info, hopefully can better tailor some troubleshooting things you can try.
Roku Community Streaming Expert Just another Roku user... I am not a Roku employee. Insignia RokuTV, Ultra 4660, Premiere+ 3921, Express 4k+ 3941, Streambar 9102