Spotlight cam no sound

I have 3 outside spotlight cameras. On 2 of them the sound is perfect and I can hear wind and bird song. On the 3rd there is just no sound. Video on all 3 is perfect. I also have 2 indoor cameras which also work perfectly Could it be that the system is overloaded for sound on the third outside camera?Wi Fi throughout the house is perfect and high speed by the way Thanks for any advice