Upgrading Data Type of Active Processes

We are on 17.1 Cloud.

We have a process model M (Main Process Model), which calls another process model S (Sub Process Model). Now, we had to modify a data type (Custom Data Type) of one of the parameters of process model S. Of course, there would be corresponding change in the main process model M. After the changes, new processes would work fine. But, for any processes initiated before we made changes will face issue of type mismatch when S will be called from M. So, to counter that, is there a way I can modify the custom data type of existing processes?

I hope there is a way or a solution of making Custom Data Type backward compatible.

Thanks in advance!

Akshar