We were facing an issue today; the issue was something like this
We were sending mail in one of our workflow, in the to field of the workflow we had set multiple users name as dynamic values. But we found that mail was being sent to only one user, i.e. the first user only.
Than we found out that if we add multiple values in Look For dialog box and click on ok to add all those together, only the first field having value would be picked by workflow.
For e.g. if I add (created by), (manager of the user field) in the look for dialog box and click on ok to add them together, the workflow would only pick the value for first field i.e. (created by) field for which value exists. It would ignore the manager of the user field.
However if we add them separately i.e. first add (created by) field and then look for (manager of the user field) and add that field than we could have values for both the field.