SharePointFramework: unable to load main WebPart component when it contains code to load jQuery

You are using ModuleLoader which has been long deprecated.
Instead of that you should be using SPComponentLoader

Add the below import statement:

import { SPComponentLoader } from '@microsoft/sp-loader';

And modify your code to:

SPComponentLoader.loadScript('https://code.jquery.com/jquery-2.1.1.min.js', { globalExportsName: 'jQuery' }).then(($: any): void => {
this.jQuery = $;
SPComponentLoader.loadScript('https://code.jquery.com/ui/1.12.1/jquery-ui.min.js', { globalExportsName: 'jQuery' }).then((): void => {
this.renderContents();
});
});