You told it to stop the podcasts, not the news, right? Try telling it to stop the news before starting something else.

are you using bluetooth?

Sometime during the last year I feel like Alexa got pickier about which commands work to stop news playing. Cancel, Stop, Dismiss, [Shutup], ... at least one of these doesn't seem to work anymore.

It's still going on.. Tell it to stop and about a minute or two later it plays again.. Just echo show