Tremolo playback bug in orchestral template

Playback of tremolo strings appears broken in some situations, in MS 4.5.2

Marking a minim with quaver tremolo should playback exactly as it would if we just write 4 quavers. In Test_4.5.2b that's what happens. That score was created by selecting the instruments individually.

However, Test_4.5_orchestra was created by choosing the Symphony Orchestra template, and you can hear that there is a big difference in the sound, particularly the D-F tremolo. The use of tremolo notation for strings is very common, so this really needs to be fixed - can't go through life writing lots of individual semiquavers!