Got an odd issue with a 4-element M2 6M5 on 50 MHz. SWR is flat as a board (1.1:1) in horizontal polarization but shoots up to 3:1 when I flip to vertical. Everything looks physically sound - elements are aligned, connections tight, boom level. Using Type-N connectors at the feed point. Anyone seen this asymmetry before?

Ground plane should be adequate at 50 MHz - the tower's metal structure provides plenty. Feedline is RG-213 with good velocity factor specs per manufacturer.

Check your gamma match assembly carefully. Gamma matches can develop intermittent connections that affect one polarization more than the other. Also verify the driven element isn't bowed or twisted - even slight mechanical stress can cause polarization-dependent SWR issues.

M2 antennas typically use quality hardware but I'd suspect the relay or switching mechanism first. If you're using a relay to flip polarization, swap it with a known good one. The contacts might be making poor connection on one side.

Had similar issue on my 2M yagi. Turned out to be water intrusion in the feed assembly. Use dielectric grease on all connections and check that seals are intact. Also measure DC resistance across the driven element in both orientations - should be identical.