This happened before (issue) and was fixed (PR), but it's happening again. I'm suspecting the issue might be because internally CanvasKit doesn't track which context a particular resource is coming from. WebGL, unlike OpenGL, does not allow sharing resources across different contexts, so when we use multiple contexts resources need to be rebound to the currently active context before drawing.

Skia issue: https://bugs.chromium.org/p/skia/issues/detail?id=12255
Internal issue: b/197480079