I have a Production Power Automate workflow that has been running successfully since August 2023.
There have been no recent changes to the flow or the associated SharePoint list.
Suddenly on the morning of Oct 18, 2023 (9:02 AM Arizona time) I begin seeing workflow runs Fail.

I investigate and find that they are all failing at the same SharePoint Update Item action.

This Update Item action has worked successfully since the workflow went live in August.
As a test, I remove the action and re-submit the item.
This time it fails at the next Update Item action it encounters. An update action that has always worked previously.

All of the failed workflows have the same (or similar) error message at the point of failure.
Exception from HRESULT: 0x80131904
clientRequestId: d15a1951-4a50-46a9-8f20-ffdd914e8075
serviceRequestId: d15a1951-4a50-46a9-8f20-ffdd914e8075
{
"status": 400,
"message": "Exception from HRESULT: 0x80131904\r\nclientRequestId: d15a1951-4a50-46a9-8f20-ffdd914e8075\r\nserviceRequestId: d15a1951-4a50-46a9-8f20-ffdd914e8075"
}
Note: Only the clientRequestId and serviceRequestIds were different between the error messages
The SharePoint Online list only has 163 items in it.
There have been no changes to any of the columns in the list.
Fields that are updated are the InstanceURL, Status, WFState, TriggerWF, and Workflow History, etc., which are Single Line text or Multi Line text fields.
The workflow has previously been able to update the SharePoint list.
There are about 150 workflows running at the present time against items in the SPO list.
Does anyone have any idea what might be causing this issue?