iFrame Chat window eating mouse events? How to fix?

I have a 3D (unity) webGL-based content app which underlies HTML UI, and a Jitsi iFrame sits on top of all that. My issue is, when I have ‘Chat’ enabled, I cannot interact with my webGL content. It’s like the iFrame (chat) is swallowing or disallowing mouse interaction outside itself, although other HTML items are still interacting. Just the webGL content is not.
Has anyone seen this, or have any clues why? or how to get around it?