Can't watch videos with the browser - play, stop cease to function

Can’t watch videos with the browser - been a problem for about a month
do this as one of many examples
go here http://www.synthtopia.com/content/2017/02/06/audio-connectivity-with-modular-synthesizers/
play then stop
go you tube
press stop, then start, then stop then start, soon none of the buttons work - all gets clogged up
on occasions you can’t exit the tab via the ‘x’, other times you can’t exit the browser via the ‘x’
total mess and unusable

https://forum.avast.com/index.php?topic=196529.0

Well… i’m not quite sure what this is a same thread. He’s talking about a… “month ago problem” (not the problem after update) + a bit different… symptoms.