I found weird problem with Nintex workflow running on one of my lists on SharePoint 2010. There is a conditional startup set when items are modified and it works fine but runs twice.
I checked whether something changes this status on update, but no. All the other workflows work fine, so the problem isn't in configuration or duplicated scheduler. List was not moved and I was told it worked fine few months ago.
How can I diagnose what's wrong and how to fix it?