We have a workflow that is supposed to assign an approver and send a task email based on a value in a dropdown. The emails are pulled from a lookup list. The workflow has worked as expected nearly 100% of the time, but a handful of submissions from different users have failed to pull the email from the lookup list, either leaving it blank or throwing the error #value!. This suspends the workflow, but when I restart it, the value pulls correctly and the workflow resumes. What reasons could account for this error that happens so sporadically, and how can we prevent it? We use O365 SharePoint.