Everything was working fine until the latest update to Fire OS 126.96.36.199 (NS6253/1437) got installed on the 31st July 2018.
Now frames are very visibly dropped in both Prime Video and Netflix, to the point that the experience is so dissatisfying that I have to use my MacBook + HDMI to watch those videos.
I contacted the Amazon helpdesk and after over an hour in chat with 3 distinct operators, they completely failed to correlate the software update with the issue I am experiencing, despite the absolutely perfect timing. Also, it can't be a coincidence that the main feature of the update is the "Matching Original Frame Rate". It's just an obvious deduction that a bug has been introduced in a critical part of the playback code.
Instead, I am asked to reboot the device (fair enough), clear the data/cache of the apps (fair enough), check my broadband speed (really? the videos work perfectly on the other devices on the same network, I tell them to no avail), reboot my router (really?!), and reboot the device, and so on.
And at the end of a stream of useless steps, I am proposed a replacement device. To be noted that I had (like many others) similar issues with 3 other devices (Fire TV stick) but the 3rd gen Fire TV worked like a charm until two days ago, the day of the update.
Apologies for the rant.
Anyone experiencing the same problem since the update?