The trio is in a separate flow from the music which precedes it, and the Gap between flows during playback is set to zero in Library > Playback Options > Timing. The repeat marker at the end of the piece is actually a D.C. al Fine with custom text which makes it look like D.S. al Fine. The segno at the start of the trio is actually just staff text using the SMuFL glyph U+E047 and not a repeat marker. The piece ends at the Fine after the second ending, but Dorico does not allow two repeat markers to be created at the same rhythmic position, so I changed the rhythmic grid resolution to a 32nd note and moved the Fine to the left by pressing Alt/Opt-Left Arrow in write mode. To skip over the second ending once the first ending has played, there is a hidden D.S. after the first ending and a hidden Segno after the second ending.