SharePoint Designer workflow error:
The workflow could not update the item, possibly because one or more columns for the item require a different type of information.

If you look at the workflow history nothing of value is there to clue you into what field is broken.

To track down what field is broken, I added a Pause action to my Step. Then I added a Log message before each action. Doing this helped track down the broken field.

Once you get the workflow working again, remember to clean up the added Log actions.

In my case, the workflow was trying to update a Person / Group field with an employee that no longer worked at the company.