Changes to the simple heat exchanger interface (TL)?

I have a Simulink model that uses the simple heat exchanger interface block. This model runs perfectly fine on MATLAB 2018a, but I currently only have liscenses for Simscape in the 2019a version so I must use that if I want to update the model. However, when the simulation is run in 2019a, I come up with this error:

Error compiling Simscape network for model Water_Heater_rev_08.

Caused by:

Number of equations exceeds number of variables. Click on any Simscape blocks identified below for more detailed diagnostics.

The only block provided as an option is this simple heat exchanger. Was there some kind of change to the block in the new update that I have to account for? Or has anyone else run into this problem and found a solution?

[Martin]

I would encourage you to contact Technical Support with a copy of your model.