I have flash briefing called "BART Advisories". Normally, it's a really short - it just says"No delays reported". This works fine on audio Echo devices but has issues on the Echo show (tested on the original, the Show 5 and the Show 8).
On the Show the briefing plays fine, but at the end the next flash briefing does not play. I need to say "Alexa. next" to exit the Bart Advisories briefing to continue on to the next one.
I believe the Show has an issue with really short Flash Briefings. Sometimes the breifing is longer, and when it is, it works just fine on the Show.