Pressing multiple keys on GarageBand's "musictyping" tool sometimes doesn't work correctly

"Musictyping" tool in GarageBand enables us to use keyboard of the PC as the instrument keyboard, but when some specific set of the keys (listed below) are pressed at the same time, some notes won't be played:

vertically close 2 alphabet keys + another key : [AWS],[AED],[STG],[SYH] etc.,

alphabet key on the QWER-row + U + ; : [WU;],[EU;] etc.,

alphabet key on the ASDF-row + J + ; : [AJ;],[FJ;] etc.,

and many others.

I'm using Makbook Pro. It's not expected that multiple keys will be pressed at the same time in the normal situation and that tool is just a supporting function, but I will be glad if you share any ideas to solve this problem or (if developers are reading this,) improve this spec.

Thank you.