AEP schema creation error - "Cannot merge incompatible data types"

I am not too familiar with the XDM schemas, but this looks like a type mismatch...

It seems that the schema may be looking for a datetime stamp? Perhaps the app is sending as string? Maybe this is a simple as casting the string as datetime before applying to the schema?

I am guessing there is already data coming into the schema in that field which may be preventing it from being edited?

Adding to what Jennifer already shared w.r.t. the data types, you might also wanna check the below scenarios.

- There could be the same field defined in your tenant by someone else with a different data type. Please try renaming the Field name(not the Display name) with correct data type as required.

- You will not be able to edit your previously defined schema that has been used in the Platform if you're trying to bring in a breaking change. However, you should be able to do so if data is not yet ingested into that schema.

Here is a link from the documentation explaining the supported and breaking changes to an XDM schema  - https://experienceleague.adobe.com/docs/experience-platform/xdm/schema/composition.html?lang=en#evolution 

I pulled the batch using the API and it gives the error code but also the exact data can be seen.