I had this problem and was able to resolve it with the declaration below.
$.fn.bootstrapBtn = $.fn.button.noConflict();
首页 > 技术文章 > jQueryUI modal dialog does not show close button (x) JQueryUI和BootStrap混用时候，右上角关闭按钮显示不出图标的解决办法
haoliansheng 2016-08-02 22:17 原文
I had this problem and was able to resolve it with the declaration below.
$.fn.bootstrapBtn = $.fn.button.noConflict();