I had a similar issue that looked like a breathing blurry glitchy effect on just one of my foliage meshes, which was happening on every instance of it.
Turned out that on some of the materials for the mesh, ‘advanced wind’ was ticked and on others for the same mesh it wasn’t. so I ticked it on each material and it solved the issue. This was on one of the quixel megascans beech trees. I’m not sure if it somehow got unticked or it came like that when I downloaded it… I’m guessing the conflicting wind setting on the different material layers were making an artifact visible.