The internal 15psi limit is, in some ways, a good thing. I say it's a good thing because it's one limit that is absolutely critical because you absolutely want to know when the oil pressure has dropped. As a result, GRT has taken away our ability to screw up this setting, thus it's something one can depend on! :-)
I do hope you get your issue sorted out, Sean. The good news is that GRT is, even in this covid environment, turning things around pretty quickly.