Infinite loading of the cash register after reload

I have tested WebPOS more intensiv and got a new error.
I added a product to the cash register and reloaded the web page by mistake. After that I get an infinite loading of the cash register. So, I checked the developer tools and saw a JS fatal error which prevents the cash register to finalize the reloading process. Please see the image attached.
We have planned to switch the live website to WebPOS in one week and I’m worried about the problems I’ve discovered in the meantime. Because something like what happened to me during testing could also happen to the cashier. And then the cash register can no longer be used.