Some very creative programming going on in Dorico Pro 6.2.3.
An unslashed quaver grace note leading to a crotchet plays a quaver followed by a quaver. This seems apparently correct, as it is.
An unslashed semiquaver grace note leading to a quaver seems to play a rushed demi-semi-quaver followed by a dotted semiquaver.
I have investigated this further, as see below.
Has anyone else found these phenomena … and are they ever likely to be fixed?
RT
As grace notes are ornaments, they are not played in exact time values. Instead sort of garnishing the main music.
In classical music a grace note with longer values like 1/4 or 1/8 might be played on the beat, thus taking time away from the next note.
If you see a 1/16 or a crossed through 1/8 grace note, then it might be played before the actual time beat, thus taking time away from the previous beat.
This sounds quite theoretical, but actually someone like Mozarts father said, the distinction would be so easy, that any whistling farmer would do it right by instinct..
I didn’t have time to check your examples, but I will try later. I personally wouldn’t bother too much about the playback of them, still thank you very much in discovering and pointing it out.
I tried your examples:
Untitled Project 71.dorico (1.7 MB)
And yes semiquavers before dotted crotchets play longer. But hey, they are ornaments 
Dorico is treating the unslashed grace note as an appoggiatura, which when followed by a dotted note usually takes two-thirds of the dotted note’s value. If you don’t believe me, do a Google search for appoggiatura before dotted note.
I am OK with the appoggiatura (having done further research)
BUT now I have semiquaver or quaver grace notes leading to crotchets that are supercharged to about 37 Bar … in a piece whose tempo is “Grave”.
They sound like absolute something not very nice at all (or at least explosive something-elses).
Here’s what I have to do to make them sound like music, rather than explosive thingumy-whatsit (or worse).
I even have to use three levels of slur to get them to play smoothly.
Oddly enough, these ones sound all right …
It also seems all right with the trill on the middle note. The problem here appears to be the combination of trill on the first note and grace notes on the third …
The following sample sounds OK, but in the first sample (with the trill on the first beat) the grace notes are extremely rushed in playback.
These also benefit from slowing down:
Unfortunately your appoggiatura argument doesn’t seem to hold up in the following case:
The grace note is again rushed at hypersonic speed (in my work-around you can actually hear the grace note).
And while we’re at it, why does this not play anything until the quaver?
Thankfully I have managed another work-around:
RT
Somebody well-meaningly suggested somewhere that I can vary the length of the grace notes in the midi play view, but I still find it hard to accept the logic of the glaring inconsistency of the default values adopted in the following examples attached …It appears that something in the placement of the trill is causing distortion of the logic governing grace note definition. I hope this is helpful to somebody willing and able to pay attention to something that is apparently such a minor quibble.
