Flashing Mips in Virtual Textures

We’re pushing virtual textures pretty hard in our 4.27.2 project (120 32K textures, 180+ 8K textures). Everything has worked reasonably well until the last 20 or so maps…

Doe anyhow have any thoughts on what causes flashing mips or if there’s anything we can do to reduce it (besides the obvious solution of using smaller maps…)