Trill interval changing when Condensing enabled

No idea. I note that manually setting the interval in the properties panel (for both clarinets) to Minor 2nd fixes it.

As to using Accidentals rather than Hollywood, there’s a long-standing bug with Condensing whereby they’re always calculated as though the first note were on the middle staff line (a B in treble clef, a D in bass clef etc.). That’s a pain for which there isn’t currently a good solution (though if you’re really in a bind there’s a laborious way to cheat it: Bug with Trills in Condensed Score - #18 by pianoleo)