Hey there, If you could share the callstack or logs or anything that could be helpful. Testing locally, I’m not seeing this an asserts with default 5.6 and the current Mutable Sample. Do you have any engine edits or custom assets in your test sample project?
For the Mutable Sample, we haven’t updated it with the 5.6 version yet, but we will soon. There have been improvements to Mutable, but you would have gotten those improvements when downloading 5.6