Help! JVB using VP9 simulates LastN=1 for some attendees some time... not predictable

For no apparent reason (under great network conditions), some attendees (but not all) in a multi-party meeting (e.g.,7 people) will see everyone in tile-mode freeze except for the dominant speaker. When someone new becomes the dominant speaker, the new dominant speaker starts moving and everyone else is frozen.

It is as if LastN was set to 1, but we have LastN hardcoded to 16 for all meeting sizes.

We aren’t seeing this if we use VP8, but we can’t use VP8 because VP8 doesn’t handle packet loss nearly as well as VP9.

It feels as though we’re missing some setting – unless we’re hitting a bug in VP9’s layer-forwarding or BWE-respect logic.

Any thoughts?