Can confirm this behavior. The If node behaves even weirder (it channels all errors to the false branch along with the items that properly fall there due to the condition).
Looks like the best workaround for now is add extra logic past the Set node.
Note that the If node in this example is configured to always return data to not stop the workflow if errors is all you have.
See this discussion on a similar matter:
If this workaround makes sense, please mark this post as a 
Solution.