Problems with a violin line
In the attached file, which contains several versions of an excerpt of a larger score, there are two basic problems.
1) Notes A5 and Eb6 (and probably others, I haven't made further tests) have a parasitic rythm, probably caused by an exagerated vibrato. I've exported the file as wave and examined it in an audio editor, the vibrato seems to be 10 dB in amplitude (max - min) which is more than enough to be perceived as a rythm. It is particularly noticeabe as repeated 16th notes at a tempo of 120. If the note is sufficiently short, the parasitic rythm disappears. If no rhythmical reference is present, it my be unnoticed. I guess this problem may be asociated with the soundfont or with the synthesizer.
2) There is a confusion as to what marcato and accent mean, and as how different articulations combine. Marcato and accent are intensity emphasis articulations, so they should not affect the duration of the note relative to the full theoretical duration. See for instance the definition from Wikipedia (https://en.wikipedia.org/wiki/Marcato): "Marcato (short form: Marc.; Italian for marked) is a musical instruction indicating a note, chord, or passage is to be played louder or more forcefully than the surrounding music.". While it is true that in certain ocasions it may imply a slight and brief tempo slow down, it mainly affects intensity (and anyway a tempo change has nothing to do with shortening the note and keeping the beat). None of them does so in playback. Accent really does nothing, and marcato reduces the duration to 67 %. When combined with staccato, which is indeed a duration articulation that reduces duration to 50 %, both accent and marcato do cancel the staccato, yielding 100 % and 67 % duration, i.e., converting staccato in tenuto and portato respectively. Intensity and duration articulations should combine independently since all combinations exist in musical performance.
NOTE: I know it is possible to tweak things combining the use of the piano roll and the inspector, but it would be better if by default one got the standard behavior, for instance an accented staccato could imply a velocity increase such as 10 or 15 with a 50 % duration.