Blame it on that cheap thermometer, man. I had the same thing happen with a pork shoulder where I kept cranking the heat because my thermometer said it was stuck at 150, ended up with dry meat.
Wait you cranked it to 150 and it still came out dry? That's wild, I thought pork shoulder was supposed to be bulletproof even if you mess up the temp a little. I've been running my pork butts low and slow forever, never had that kind of disaster even with a janky probe. Guess I got lucky with my cheap thermometer so far lol.