Noticed VL throws an error when you try to set a spread of bools to bangs, see this gif :
This happens from 2019.2 0126 onward.
EDiT : still the case on latest preview (0321), seems that changing the button mode of a
Spread<Bool> to bang also changes the type of the IOBox to
Bool, hence the type mismatch.
The middle-click inspector still displays Spread related stuff (maximum visible entries, etc), even though the type is set to
Boolean. Current workaround is to manually set to
Spread<Bool> again to get a spread of bangs.