Trouble adding new collar to alpha

[Walker 204]

I got a second collar for my alpha system and added it according to the instructions. It paired up just fine but after doing so my first collar now had no contact with receiver, all signal was lost with first collar. So I reinstalled 1st collar just as I did with 2nd collar. Now 2nd collar had no signal. I reinstalled 2nd collar under different name and receiver said info was already there so I deleted new name then both collars had a signal. Did I do something wrong or is it a problem with the system? Has anyone else seen anything like this? I will admit that I am not a very tech savvy person so it would not surprise me if it is my fault but would like to find out what was wrong. Thanks for any help.