Flash (in FF49) gone capute?

I don’t know whether FF49 has had a minor update, or what. But I have noticed several websites hang because flash is active.
The sites are
BBC News after you click on a video, website hangs
Sky TV does not load page and hangs
Plusnet Community as Sky above.

If I deactivate Flash then all these websites load normally
I have tried the websites in Chromium and they work perfectly.

Could someone confirm this is a bug and I can report it to Mozilla.
You will need to be running a fresh upgraded version on 16.04.1 and an AMD APU or GPU with the beta supergpu driver.
Firefox 49.0
Ubuntu Mate 16.4.01 lts 64bit
Kernel 4.4.038-genericx86_64

If it is not a bug, what could it be? any help (as usual) greatly received.

Sites mentioned work OK on Intel and Nvidia GPU. Sorry I don’t have AMD set up to test.

Have you tried altering the window manager (compton/marco/etc.) to see if this is repeated?

Flash has been updated and the problem has gone.