Here is the root cause. It is due to the difference between R2020b and earlier versions. You have to figure out how to deal with it.
The output line of a "Bus Selector" block is not suppose to be able to set its signal name or "SignalPropagation" property, because the signal is "selected" from the bus. It is not meant to create a new signal.
In earlier version (e.g. R2018b), the "SignalPropagation" is set as "off". You can run set(LineHandle,'SignalPropagation','on') command but it has no effect. The property value is still 'off'. The command does not cause an error.
In R2020b, the same command caused the error message you saw.
Possible solution:
- Add a "try" "catch" statment to catch the error.
- Check the "SourcePort" property, which can tell you it is a "Bus Selector" block.
