For what it's worth, I've occasionally noticed similar problems with frames (embedded content from other sites especially), and it seems that force-reloading th

For what it's worth, I've occasionally noticed similar problems with frames (embedded content from other sites especially), and it seems that force-reloading the page with ctrl-shift-r gives a different behavior than the reload button in the uMatrix panel. I usually unblock the embedded domain, manually allow frames, then force-reload the page, but it usually seems to work.