Wifi speed unstable after battery change

I recently changed the battery on my Macbook Pro retina late 2012. The problem now is that my wifi connection is really unstable. At first I had no wifi and bluetooth at all, and found out that it was probably some issues with the i/o cable. I reattached the i/o cable again and now I had both wifi and bluetooth connection. But…

After using the computer for a while I found out there was some problem with the speed and connections with both wifi/bluetooth. Can it still be i/o cable , or is it maybe the airport card/antennas – the antennas are a little bit loose.