I've got a simple workflow that uses a single Request Data action to get some information from project managers, there are no escalations or reminders setup. I use a site workflow to update a column in this list that triggers the workflow on each item (an easy way to trigger workflows on multiple items). A single workflow starts for each item, however the Request Data action inside the workflow has created 4 tasks for each item, therefore sending 4 emails for the same thing to each project manager. Also, only the last task in that sequence actually works, the others give an error when accessed:
and when I look in the ULS logs, it says "Cannot find a corresponding human workflow task ID for this task". But if I go to the list they are there but inaccessible.
I have seen this document Workflow performance improvement and load reduction which does mention this error, but it says that it happens when the workflow is too big. This workflow is 187kb.