It seems like only 6 keys can be pressed at the same time? (Using Construct 3) any additional key is not detected until one of the first 6 is released. Anybody has any experience on this?
It's quite possible this is a keyboard limitation. For example, my SP4 can't recognize if I'm holding shift and press the left arrow key at the same time.
Keep in mind this is hardware-specific (but can also be limited by software), and expecting users to hit more than two or three keys at the same time is outside of standard keyboard usage.
There's a test app at the top of this article to see what your keyboard supports: