5G Home internet keeps dropping!

It is hard to say for sure. Maybe it is related to congestion on the tower and traffic throttling or possibly it could be another source disrupting the traffic. 

Do any of the cellular metrics fluctuate significantly during that period from when the traffic works?

Performance can be seriously impacted due to signal noise. Watch the RSRQ, signal quality and the SINR, signal noise. It might be some noise that results in significant impact on the signal. If you are in an urban area where there are more potential sources of RF noise I suppose possibly there could be a relationship to some factory or possibly a distribution center.

In addition to recording the cellular metrics you might experiment with the orientation of the gateway just a bit at a time. I discovered that by rotating the gateway clockwise or counter clockwise the exposure of the antennas in the gateway of course is different. There are multiple antennas in the Nokia that are in an alternating pattern with the cellular - wifi - cellular - wifi … orientation. As you rotate the gateway you can expose different antenna to the signal improving the signal wash over the antenna. I found by rotating my gateway pretty much 180 degrees from my initial placement to having the backside facing inside the room the signal receive power improved 2-3 dBm and signal quality also improved. It was a minor change but did result in a bit better performance. 

On the back side left and right of the LAN ports there is the 5G-4 and 5G-1 antennas. Directly across from the back is WIFI-4 and to the left and right are 5G-3 and 5G-2. From my tinkering I found exposing the 5G-3 and 5G-2 antennas toward the window produced much better reception. I don't know quite why that is but it did make a difference.  If the exterior shell is removed the labels on the antenna are clearly visible. Those two antenna exposed more direct toward the tower make a difference for me.

Another possible thing to consider would be some transient signal on the power line. It might be rare but with power conditioning it can be prevented. I run all my electronic gear on UPS systems to protect them but that also conditions the power filtering out any noise that might be on the power lines. Think about it. If you can send Ethernet modulated over a power circuit there are possible transient signals that can also ride those power lines. You often will never know what others are doing around you so identifying a source of noise without expensive equipment is pretty difficult. 

Then again with all that said it could have nothing to do with the gateway or local influence. It might just be congestion on the tower and excessive throttling. Doing things you can have some influence over to rule out local issues is a start but might not still resolve the behavior.