Meshes drawn with DrawInstanced disappear after SteamVR menu usage

As title. We’re drawing meshes with DrawInstanced, in single pass stereo. Using the menu causes these meshes to disappear, and never come back. Any ideas?

Some textures get corrupted too.

Unity 5.5.0f3.

This turned out to be due to Time.deltaTime being 0 while the VR menu is being shown. Never divide by raw time deltas folks!