Hi there, has someone tried the same problem ? Occasional lack of sound happens when I play many notes at the same time. It can be when I play the recorded track even if during recording it did not happen. I use Catalina OS on a 2012 Macbook with 8gb ram.
Lino

try to increase buffer size and use polyphony optimistic option . What happens is that  when your  audio buffer is too small, Your CPU has very little time to process each block of audio, The MIDI notes still arrive, but the audio engine fails to render some of them  and it is perceived as missing notes.
Optimistic polyphony reduces dynamically max value when process CPU exceed 75% , pessimistic option uses 50% as a treshold).  CPU is a queuing device so matter which OS you use , queuing starts to be noticeable when usage is greater than 60% . Until I move to Mac silicon I used an old late 2013 MacBook Pro , and I had glitches and drop outs with some presets , when several mics and FX effects were added and had to use the above to fix the issues . On Mac ARM chips , CPU utilisation is ridiculously low .