I’m really not going to be able to help you with this. You need someone that knows ACF, and Twig (this is a template markup system) and a developer that is capable of digging through the code to find what is broken.
You’re not likely to find the help you are looking for on this forum.
I personally have no experience with Twig and wouldn’t know where to begin debugging this.
The only other thing that I can offer is that there is probably some JavaScript that controls how this works and it is this code that is no longer working correctly for some reason.
