I have a ship I put into orbit around Mun. Playing a science game, I do not yet have the Tech Tree unlocked for the Mk1-2 pod, so I'm using 2 Mk1 cans stacked on top of each other. The top-most Mk1 can has twin Comm 16-S antennas. There is an MPL-LG-2 lab incorporated into the ship. Both Kerbals sent on the mission are scientists. Orbiting Mun along with this 'science station' are 3 Comm relay ships with twin HG-5 antennas (500km orbit)... so comm path isn't an issue. Power isn't an issue either, as adequate battery and solar are present.
The odd behavior I'm seeing is when I put both scientists into the lab; I lose Comm link. If I put one of the crew back into the lander can with the antennas, Comm link is restored. IMO, this shouldn't be. I'm wondering now, what if the antenna were on the lab itself? (something I'll have to try)
Has anyone else noticed antenna behavior like this?