Hi!
OSX 10.10.5, C9.5.1 (but same bug was on C8.5 in 2015), track’s output connected to the Plogue Bidule patch, in which PrCh messages switches out to different instruments.
A different same patch, made on C++ works good with any number of letters in Expression maps, but it seems, that this patch is critical sensitive to switching speed - so, it’s strange, why speed depends on the articulation name?