While debugging in VS code in /_layouts/15/workbench.aspx, when the web part loads, the file localhost:4321/{name of web part}-web-part.js is shown and the execution breaks on line: if(typeof Symbol !== 'undefined' && Symbol.toStringTag)
in function:
/******/ // define __esModule on exports
/******/ __webpack_require__.r = function(exports) {
/******/ **if(typeof Symbol !== 'undefined' && Symbol.toStringTag)** {
/******/ Object.defineProperty(exports, Symbol.toStringTag, { value: 'Module' });
/******/ }
/******/ Object.defineProperty(exports, '__esModule', { value: true });
/******/ };
F5 continues OK