In a score for (jazz) orchestra I'm working on, I put four hi-hat beats before the start to get the tempo.
All was fine with my computer and his synth.
With my great surprise, when I connected an external keyboard via an USB-MIDI converter the third beat, and only that, was syncopated!
I checked a rechecked everything with no avail.
My hypothesys is that it's a case of MIDI overload. Too many MIDI messages.
Indeed, removing some instruments all becomes regular.
Sic! :o
Maybe the USB-MIDI converter is a bottleneck?
Possible, in special mode if for some reason (like a glitch in my old computer) the connection is in USB 1 mode.
Sometimes my computer says, with a USB memory stick, "the device could operate faster if"... (I don't remember the suggestion) even if the socket is always the same.