Question:
When we connected the modem more directly to a specific meter, it started working. I notice there are 17 meters connected to the Block 7 modem where the problem occurred. The general rule is, of course: the less meters per modem, the more reliable. How many meters does Elster advise customers to put per modem?

Answer:
The general rule is 10 meters within 10 metres, so I think the best option is to split these meters to two (2) modems.

Good day Rudie
Yes the Rule for RS232 communications are 10 meters within 10m.
You can use a EBuf to extend this to 20M and place on after every 10 Meters.
This will keep the costs down.
Please only use a maximum of 35 meters per Modem.
The total time to read all the meters one by one increase exponentially.
I Hope this Helps