[amsat-bb] SO-50 dropout?

I took a couple month hiatus over the winter (since I was under 10 ft of snow), and now I’m back working SO-50 from work, and ramping up on the linear birds in the evening. On the last two SO-50 passes I worked (one “overhead” Saturday night, and one at 25deg an hour ago) the bird dropped out about mid-pass. I don’t remember this happening before. I use an FT530, 432-pre-amp, and Arrow antenna. With clear sky, SO-50 is pretty much full-scale. Is this antenna shielding on the bird by the bird (it has a 1/4 whip on one corner, correct)? How fast does SO-50 tumble? I am losing the 2nd half of the passes, and I don’t remember it doing that before. Bill W1PA