jQuery.Deferred exception: e.indexOf is not a function after updating jquery.min.js to latest

Question

I am using jQuery 1.12.0 and everything is working well. For optimization I have upgraded to jQuery 3.4.1 and now my slider is not working. It is giving me an error:

jQuery.Deferred exception: e.indexOf is not a function k.fn.load@https://website/js/jquery.min.js?v=1.76.1:2:83687 D/<@https://website/js/jquery.mCustomScrollbar.concat.min.js:4:20503

$(elementID).mCustomScrollbar({
  scrollButtons: {
    enable: false
  },
  theme: "rounded",
  scrollEasing: "easeOut",
  moveDragger: true,
  mouseWheel: {
    scrollAmount: 200
  },
  keyboard: {
    enable: 1
  },
  keyboard: {
    scrollAmount: 200
  },
  keyboard: {
    scrollType: "stepless"
  },
  contentTouchScroll: 200,
  scrollbarPosition: "outside",
  alwaysTriggerOffsets: true,
  advanced: {
    updateOnBrowserResize: true,
    updateOnContentResize: true,
    autoScrollOnFocus: true
  }
});

when i was using old version of minified, everything was good. As per the other link, it is suggesting that i am using $(window).load but i don't have that in my code.