What do I do to "correctly" close eM Client?

It seems that eM Client is always giving me error code that I incorrectly closed the app when I try to open. But I always click the “x” to close and I haven’t closed Windows while it is running. Recently, on several occasions, I couldn’t open eM Client at all and I had to reboot the computer. I have version 9.2.1628.0 and I’m running it on Windows 10.