Cast button in toolbar doesn't work anymore

I'm on a Windows 10 tablet and since a few weeks in all my 3 installations (Stable, Dev 141.0.3500.1 , Canary 141.0.3518.0) the cast button in the toolbar doesn't work anymore. Only option I have now to initiate casting is with: Menu-Button => More Tools => Cast Media, which is quite annoying. 

Could someone from the developer team please take a look into that? 

Thanks in advance!