Unclear error message for Swicth-Case Action on model update

The error message "The action port on subsystem '......../Chip1_WriteBytes1' can only be connected to an If or Switch-Case and may not be connected to more than one If or Switch-Case" is raised whe updating the model with the following diagram.

It would appear that each of the individual cases is only connected to one action port in one subsystem, so the reason for the error message is unclear.

Can anyone shed light on the reason this error is being raised.

Answer 1

[Graham Cotgreave]

Loss of access to the reference sub system location caused all the connections to become 'disconnected' even though the lines remained intact. Deleting and reinserting each trigger signal resolved the warnings