I suspect my initial theory was correct. You didn’t mention in the other Facebook thread that this is 17-EDO, and the reality is that your tonality system sees D# and Eb as two separate pitches. The MIDI pitch you play on your keyboard is closer to a D# than an Eb - in your tonality system - so Dorico interprets your played note as a D#. This is also why you can’t “respell” the D# as an Eb (Opt-=) but you can use Shift-Opt-Up to change the D# to an Eb.
Please keep your posts to one place, or at least crosslink - this is now in three different places (see also Redirecting... and Redirecting...) and it’s hard to keep track.