T-Mobile 5G Home Internet Gateway slow ethernet but fast WiFi

I recently installed the grey 5G Home Internet gateway at home. When I first got it three weeks ago, I was seeing speeds of 150+ down, and 50 up on both WiFi and ethernet.

Now I am seeing roughly the same speeds over WiFi, but ethernet speeds have dropped to 10-15 down, sometimes as low as 5. Upload is around 15-20.

Has anyone else had this issue and found a solution? Or is the gateway defective? Both ports appear to have the same issue, and WiFi continues to work fine.