The network error generally means when the UI/app asks controller for data it’s taking longer than a threshold to get the data back. It does not necessarily mean a problem, it could just mean the data transfer is taking longer than usual. This can particularly happen if you have multiple devices (phone, laptop) all accessing the controller at the same time, so creating longer network delay.
You said you have firmware 2.1.9, but do you know the minor revision? The latest is 2.1.9(3). If you are not on it, you can try to update to 2.1.9(3) which may solve the issue.
The ‘unused expanders detected’ is unrelated — it just means the controller detected more physical zones that you configured. For example, it may detect you have 24 zones, but you only set 16 zones. This doesn’t mater.