Flying Cart‑ Slide Cart Drawer

I voiced this concern to this app who advised me it was a theme issue, theme developers have advised me this was an app issue. I am tired of the back and forth. When I am viewing the full cart page after clicking on View Cart in the sliding cart, 3 glitches occur: 1.) I cannot change the quantity of the item. 2.) I also cannot remove the item from the cart. 3.) The CONTINUE SHOPPING button does NOTHING. I am going to uninstall this app if this issue cannot be fixed. It makes no sense to pay for this app if they can't figure this out. This has been an on-going problem and I should be able to use this app to the full-working capacity as a paying customer. Edit: Customer service has been great. Unfortunately, the app had a few flaws such as not showing the price of multiple quantities of the same item. This was kind of a big deal for me because literally all of the shopping I do online had the cart showing the way I liked, so I knew it was possible. I am currently using an app that does what I want. There was a whole issue about the cart not working properly in which they advised that it was the fault of another app's lingering codes. Then they were upset that I left a 1 star review because it was not their fault. Okay, but when you tell me you removed the code and that "it works now" and I check and it actually does not work, I'm going to feel like it was not looked over carefully. I did not leave a 1 star review for no reason; I left it after they told me everything was fine after THEY removed the lingering code. I raised the review a little bit because it's otherwise not a bad app. But I don't have the app anymore and would like all of their lingering codes removed completely.