Hey @McMuckle 
The SFT-1200 should be able to handle it. So we should look more into the problem itself than buying another router - I would say. The Mango offers only 100 Mbps on the LAN interface, not a real competitor therefor.
You could go with a 5G router instead, like the XE3000, but then you have to place your SIM card into this device rather than using the Pixel hotspot.
So all in all, I would recommend that we will look into the issue itself.
Please follow the few steps in this thread to provide the necessary information:
The logs will be necessary as well, I would say.