Hi. It seems the bug has not been fixed for macOS, at least on my system (MacBookPro 15’’ Retina display running macOS 10.14.6). It usually happens at the second or third time I apply a processing. After that, I am not able to use any function in the program and the box (which is gray on my system) will not go away. I have to force quit the program because it is not possible to quit it in a normal way. This happened every time I tried to use SL and makes it actually unusable for any audio processing. Very frustrating. SL version 6.0.1.