It's likely some inconsistency in the specified initial conditions that's causing this. The model is large and seems to contain customer specific information, which may make it inappropriate to discuss further on MATLAB Answer. Do you have access to MathWorks support team? It may be a good idea to continue through that route.
If you'd like to continue with MATLAB Answer, it'll be helpful to include the two "separate" models that initialize quickly. It's hard to read the picture and separate the model manually. It's possible to record a full set of initial conditions and ask Simscape to initialize from that. The set of data from different sources can be combined/merged, too. More info:
