Review on Waveshare 4G HAT Raspberry SIM7600G H by Jeff Johnson

I was actually hoping to use this product to make my own Raspberry Pi 4 powered mobile phone. At first everything seemed great. Ubuntu already enabled kernel modules for this and it was recognized immediately and I was able to set up an internet connection right in the Ubuntu Settings app. Sending AT commands to perform all actions (SMS and phone calls) also works great. However, when I try to do everything at once, I keep encountering problems. It's not just AT command multiplexing. The device goes into bad state when all of a sudden nothing works and I have to turn off the Pi completely and short out the HAT so it can clear every state. Then when I boot everything back up everything works again for a while. Too bad it can't be reliable enough for everyday cell phone use. The support team was quick to respond, although their answer wasn't that helpful. I still really appreciate the effort, especially the quality of my question/post I posted. Maybe they have any advice on how to fix this? I'm thinking about abandoning the project altogether or trying SixFab's LTE-M board instead.