Hello there,
I encountered the same error today, after I introduced the data validation on my main column, "S/N".
My flow basically generates a custom document after you create a new element in a list, and this next part was the one giving the error.
The "Create File" part returned "Error 400: bad request", and wrote something about "List data validation".
The column "S/N", which is the only one that has data validation, can be found in the List, where the user inserts some values like the S/N in question, in the Document library where I was generating the new files, and in the template I was using as a base for the documents.
I really wanted the data validation on this field so I refused to remove it from the input section, which is the List, but I solved the problem by removing it from the Document Library and the Template.
Because the "S/N" Site Column is the same for all of my elements (Document Library, Template & List) the data validation was uploaded on all three.
Make sure you only remove the data validation where you don't need it, so everywhere except the input forms!
Hope this can help someone 🙂
