Bitsquare quits when I quit another app window sitting on top

I don’t get this problem with other apps, only bitsquare…

If, for example, I open a calculator window on top of bitsquare, then when I do Ctrl Q, the calculator quits like normal but then also bitsquare quits. I don’t think it’s a key repeat thing because, like I say, I just don’t get this behaviour with any other app, only bitsquare.