Team members do not communicate with each other. Engineers do not communicate with designers and vice versa. For example, in a device with air quality monitoring, the body paint was changed to a more resistant one → VOC sensors react to the so-called outgassing and show overestimated data.
The team overestimates its capabilities and does not try to outsource expertise without being aware of the assessment of financial and human resources.
In pursuit of certain goals, the team forgets about UX and the needs of end users.
The product is made for nobody or "connected because it's so fashionable". For example, smart salt and egg shakers create more problems than they solve.
The device is not future-proof, that is, OTA mechanisms (updating over the air, on-the-air) are not worked out, there are not enough resources for major updates. In this context, I am always amused by the promises of cloud or IoT companies that promise lifetime service. It is not clear whose life cycle they mean: the life of the end user, the business activity of their company, or the work of the API?
The device does not work or does not work properly without a network connection.
The device does not work without the cloud.
The device stops working if there is a problem with partners (library/module, API, cloud service).