Thanks for your support, your suggestion saved my day! Maybe the explanation could help some other devs: In the last crash report, I've found this line: "exception" : {"codes":"0x0000000000000001, 0x00000001a6c79c04","rawCodes":[1,7093066756],"type":"EXC_BREAKPOINT","signal":"SIGTRAP"} Searching into the forum helped me again: https://developer.apple.com/forums/thread/46559?answerId=322813022#322813022 Effectively, I added MyApp's icon in an unconventional manner... Dragging & dropping it from another project. So, as a quick experiment I commented these lines: override var toolbarItemImage: NSImage { get { return NSImage(named: NSImage.Name("AppIcon"))! } } And everything worked fine 👌 Thank you again! 😊