Bests & Worsts Reviews from Amazon

I bought this total 6 of em for my warehouse. It was okay for 2 months. However after 2 months the walkie-talkie stop working if I got over more than 60 M (around 196ft). The signal got really weak and I can't hear anything. I thought one of them got broke down which happened before so I tried with the rest of them. Same thing happened. Now all my warehouse workers are complaining that they can't communicate each other. Our warehouse is not that big. It's around 40,000sqft and there is no wall in between. I'm so disappointed.