Checkout button not working in 3.2.4

[David]

After updating from 3.2.2 to 3.2.4, the checkout button in cart stopped working.
At first I thought that it is the result of my cart overrides, but when I switched the template to Protostar (no VM overrides), the behavior is the same. Besides the checkout button, the update and delete buttons by individual cart items do not work either.

Any hint from anybody?

[Milbo]

Seems to be a js error, check your java script console.

[David]

Hmm, I dont know how to debug JavaScript...

[David]

I don't understand it... When using Protostar template with no overrides, from where can originate JavaScript problems?

[David]

Well, after clicking the checkout button and other controls on the page, I get errors like these in the console:

TypeError: $(...).vm2front is not a function
http://localhost/xxx/components/com_virtuemart/assets/js/dynupdate.js?vmver=15c1b47f
Line 136

TypeError: jQuery(...).vm2front is not a function
http://localhost/xxx/index.php?option=com_virtuemart&view=cart&Itemid=121
Line 551

[David]

Finally, I found that when I uncheck "Ajax for OPC" in Virtuemart configuration, controls on the checkout page start to work normally in all templates.

Any thoughts why all this is going on?

[David]

UPDATE:
After reading this topic: https://forum.virtuemart.net/index.php?topic=134074.0, I tried the "desperate move" - checking ALL boxes under Configuration-> Templates -> Activate Css Styles & Javascripts. Surprisingly, AJAX functions started to work again across Virtuemart - i.e. including the checkout screen and the product detail screen.