$.fn.modal.noConflict is not a function - how to fix?

Question

JavaScript

Given: a webshop on Magento 2, there is a link/links on click on each page that opens a modal window.
On some pages, it is not yet clear why, the modal windows did not open, the error in the console was as follows:

Uncaught TypeError: f[b] is not a function

Here the solution to the problem is suggested - add the noConflict method.

$.fn.bsModal = $.fn.modal.noConflict();

After that, modal windows magically work without problems on the problem pages, but another error appeared in the console:

Uncaught TypeError: $.fn.modal.noConflict is not a function

And although this error does not affect functionality, I want to figure out why it does?