5G home internet keeps dropping

Do yourself a favor and use www.cellmapper.net to learn where the T-Mobile towers are. Record the information about the ones close to or around you with attention to the PCI (physical cell ID). If you go into the router with the web UI at 192.168.12.1 you will see the primary and secondary channels/signals on the overview page. That will show you the connections and RSRP/RSRQ/SNR values to know the signal strength, signal quality, and signal to noise ratio. Then go to the status page and record the band, and PCI information from the primary and secondary signal reporting. If you proceed to the "statistics" page you can select cellular and record the statistics there. See if there are packet errors or packet drops. If you have problems using cellmapper.net open a call with T-Mobile support and ask them point blank where is the tower my router is serviced by. They have the PCI information and can tell you the coordinates of the tower. You can use Google Earth and a drive about to confirm what you know and get a good ideal how to improve matters. Use your phone to locate the tower. If you use an iPhone put it into field test mode and read the PCI value it knows. Chances are both may use the same tower. It is not a given but a good datapoint. 

Con PCI information for the primary and secondary channels and the bands used you can use the information from cellmapper.net to determine where the tower is that sends to you. With this and some testing you may be able to better locate your router. Watch out for metal screens or buildings in the path to the tower. If a window has a screen that is metal either put the router above the screen or remove the screen from the window to prevent shielding of the signal. Don't just rely upon the bars on the top of the router. They are actually rather generic as vendors don't have a MUST directive for how to deal with those but a recommended use. One feature of the LED display on the top of the router is the alarms. If the router does have temperature issues it will or should report an over temp alarm. The only way I have seen to get the alarm is to use the LED display on top of the router. Forget the mobile application it is about as useful as well blah… It is very unreliable and not much value. 

If you only have say the 5G signal dropping from time to time it could well be T-Mobile engineers are working on the equipment on the tower in your area and that is the cause not the router itself. I highly suggest to not just accept mediocre service but talk with T-Mobile support engineers, try the router in different locations, get the information about the tower location and be patient. Record your findings from trying new locations and then dial it in. If you do the same thing, expect the same results. 

If I can help you understand what you see and help you dial it in I am happy to do so.