I have problem with copies topic from Lead to Opportunity. We use qualify proces and on opportunity is set workflow and topic is not copies.
WhenI disableworkfow,
topicis copied.
I do not know what exactly your workflow does, but the built in logic of CRM sets a mapping on the lead to map some of the fields from lead to opportunity. If you want to map other fields you could go to settings > customizations > customize the system
> entities > opportunity > relations > N:1 relations. And in the mappings set the required mappings instead of using workflows.