Archer C400 has 6 antennas, 3 on left side and 3 on right side.
When I first setup the router, I only noticed 2 on left side and 2 on right side (front most and backmost antenna). I missed the two antennas that are located on middle right side and middle left side.
I recently noticed the other 2 antennas (mid right and mid left). I put them up. Now on 5GHz the performance is very weak. I get 0-5mbps and it is not stable, wifi drops consistently. This issue is only seen when I put up the mid right and mid left antenna. If I put the mid left and mid right antenna, the wifi is very stable and I get 100+mbps. This issue is only seen on 5GHz.
2.4Ghz is completely fine with all 6 antennas up or 4 antennas up.
5GHz is not stable and drops wifi and slow speeds with all 6 antennas up. 5Ghz is stable and normal speeds with 4 antennas up (front most and back most antennas on left and right side).
I'm not exactly sure how or why this is happening. Is my unit defective?