Flow with multiple approvals stopped working

[Tim Goneau ✔️]

I created a flow for a sharepoint document library. A document could require review and approval from anywhere from 1 to 10 approvers. So the library has 10 columns where the user can enter up to 10 approvers (Approver1, Approver2, etc). The flow creates an approval task for each approver listed. If approver1 and approver2 are filled out and the others are left blank, only 2 approvers are required and only 2 tasks are created.

This was working magically up until today. Suddenly, Flow does not like when there are Approver columns left blank and returns this message:

BadRequest. The request failed. Error code: 'InvalidRequestContent'. Error Message: 'The request content was invalid and could not be deserialized: 'Required property 'assignedTo' expects a value but got null. Path '', line 1, position 1437.'.'.

Any ideas why this was working yesterday and then stopped working? Possible change to Flow (we're online)?

[#2]

Sounds like someone went to your SharePoint list and made one of the columns required. I'd start there and make sure that isn't the case.

[#3]

Thank you for your suggestion. I wish it were as simple as that. I double-checked and no fields are set as "required".

The approval workflow suddenly just does not like it if an approver field is left blank. Again, this worked just fine yesterday on two separate libraries and works on neither today.