This thread makes for an interesting read!
When you buy Blynk energy it’s to allow you to add widgets to your mobile device. The code libraries that @ralphrmartin suspects may be at fault are open source, so the UK consumer rights legislation isn’t really relevant to that aspect of the Blynk offering.
The Blynk guys obviously want the best and most reliable product to be available to their users, so will fix bugs as quickly as possible whenever they’re identified. There are a few threads about my project stops working after x number of seconds/hours/days/week’s, but there doesn’t to be any commonality between them and there are also a large number of users who don’t have issues and who are also using the same basic functions within Blynk.
In these circumstances, it’s unreasonable to expect the Blynk developers to take this issue further without the error being replacement capable by others, or multiple users reporting the same issue.
In this particular case it seems that the DHT sensor is the weak point and hopefully changing to a more reliable sensor is a good starting point. Possibly changing the ESP module, or running the device while connected to a totally different Wi-Fi network would be the next steps if changing the sensor doesn’t fix the problem.
If the thread was a little less confrontational then ther would probably be more people chipping-in with ideas and potential solutions. I realise that it takes a while to test, waiting 4.5 days before you know if the issue has been resolved, so maybe getting a couple more ESP devices and running them with a variety of sensors and in different Wi-Fi environments simultaneously would be a good way to move forward?