I can observe what you describe with the preset you uploaded.
As a diagnostic, load the VSL's packaged preset: 65 Horns - a8 > 01 HO-8 Preset VIPRO. When I repeatedly hit the pLeg cell ( in this case, assigned to D#1 on the X-axis and CC1 on the Y axis ), I hear it behaving without note cut-offs. Admittedly, it doesn't sound very good because perf-leg patches are not built for rapid repetition. But the last two repetitions do alternate ( a classic machine gun ), and there is no voice drop-out.
In the preset you uploaded, the pLeg cell has in slots 1a and b the Epic Horns and the Orchestral Horns (01 HO-8_perf-legato and 01 HO-4_perf-legato_fa respectively) playing at the same time. I'm not sure why it's set that way. Twelve horns? "It goes to eleven." I don't know if Jay's sequence uses it for fast-rep work ( I looked at the preset but did not upload the song ).
There may be a preset-specific issue here. If you load the standard issue preset, hopefully you'll hear the performance different that I observed.