Here is the deal, wireless is very erratic, foscam wireless is even worse..You can try to change the channel on your router for better signal (use a free mobile app like wifi analyzer to find the least congested channels) You have two options, wire the cameras up or use powerline adapters which are more reliable than wireless. What router are you using? Something with more range might help...but if you want a solid connection, you need to wire it. Its not hard..you might want to hire a professional just to run the cable, it will save you lots of headaches..
If you just bought the foscam, return it..there are lots of better options.
Edit: i see you have another post about this issue, where you are using
blue iris at a remote location. Have you tested the cameras locally to see what the frame rate is there?