Simscape: 'Cannot find a matching block state corresponding to element 7 of signals structure array'

Hi.

I am using simscape and SDO. My model runs initially with the desired initial states, but then within the SDO parameter estimation objective function, it fails with the error:

'Unable to load the specified initial state for model Cannot find a matching block state corresponding to element 7 of signals structure array'

I am unsure what the signals structure array is. Assuming it is the sdo simulator object SIM.InitialState.signals, if I compare that for the one inside the objective function, it is exactly the same as for the one which runs fine initially

If anyone can provide more insight for debugging, I will be extremely grateful.

Thanks all,