In order to stop, reload of you need work on configurable.js file:

On this js at _configureElement(), you need to remove this._changeProductImage();

this._reloadPrice();
this._displayRegularPriceBlock(this.simpleProduct);
this._displayTierPriceBlock(this.simpleProduct);
this._displayNormalPriceLabel();
//this._changeProductImage(); // remove this line

In order to stop, reload of you need work on configurable.js file:

On this js at _configureElement(), you need to remove this._changeProductImage();

this._reloadPrice();
this._displayRegularPriceBlock(this.simpleProduct);
this._displayTierPriceBlock(this.simpleProduct);
this._displayNormalPriceLabel();
//this._changeProductImage(); // remove this line

Who to do it: First,you should check configurable.js exits at your theme level means

app/design/frontend/{YourThemeVendor}/{YourThemeName}/Magento_ConfigurableProduct/web/js/configurable.js

If exits then comment the _changeProductImage.

Or if it does not exits then copy the file from

vendor/magento/module-configurable-product/view/frontend/web/js/configurable.js

then paste at

app/design/frontend/{YourThemeVendor}/{YourThemeName}/Magento_ConfigurableProduct/web/js/configurable.js

Do comment _changeProductImage.