Hoping someone might be able to lead me down the correct path because I'm grasping at straws here
Context:
We use the web api to create an Account & Opportunity record, and tie them together in a business process flow.
Problem:
For records that are created via the above method, whenever the user in the Account portion of the BPF, if they try to go back a step they are met with a UI dialog error
"UciError: Cannot serialize request: Cannot serialize a request with no attribute metadata for mtc_creditbpf.a_37cf930a1e09eb11a813000d3acb4d13.parentaccountid"

You would think that 'parentaccountid' would narrow it down, but we don't set it on the Account record via the web api and it's fine to be null.
Note that this only seems to happen when the user tries to transition back a step, going fowards is fine. However once the user receives teh above error when going backwards, you tend to get the error when both going to the next step or back a step
Full text of the error:
Error Details: UciError: Cannot serialize request: Cannot serialize a request with no attribute metadata for mtc_creditbpf.a_37cf930a1e09eb11a813000d3acb4d13.parentaccountid
at i (z.dynamics.com/.../app.js
at new d (z.dynamics.com/.../app.js
at da (z.dynamics.com/.../mds.js
at async ua (z.dynamics.com/.../mds.js
Activity Id: 129e9fd7-0499-40e7-a235-f9187377d89d
Happy to provide more detail if needed