I believe I have finally tracked down the cause of the null pointer issue, it was a compiler issue -- which explains why I could not replicate it myself. New release is rolling out to Google Play now. Please test and submit diagnostics if you encounter any problems. Thanks for all of the help and feedback!
Got a Samsung Galaxy A13 5G. It's Dual SIM and I have a cheap Boost Mobile 2GB plan for mapping AT&T in one SIM slot and an inactive T-Mobile SIM in the other but it still connects to the network. Now I'm able to map both carriers at the same time. So glad to be back in action lol.