[Fixed] Update 2:
As it turns out, there’s a weird bug going on that has been previously reported here: https://support.prodi.gy/t/cant-use-upper-case-label-in-patterns-for-ner-teach/719/16. Prodigy does not play nice with uppercase labels, and oddly, the solution is to use lowercase labels in the patterns file but leave the label as uppercase while writing out the prodigy command in the terminal.
It has been fixed for me for now, but this behaviour is worth looking into.