Everytime I try to sort a collection in a document template's mapping I get the error "System.Inval

Hello. I've done a document template and I mapped all the entries that I needed. That worked just fine. But then, I've tried to sort the items of the collection that I'm showing in the document and every single time I pull the connector from the collection entity to the sort one I get this error "System.InvalidOperationException: Collection was modified; enumeration operation may not execute." and then Bizagi stop working. Can someone help me? I've searched and it seems to be a problem of C#, when adding or removing items in a collection. But I don't know wich task is doing that and how to fix it. Bizagi Studio version 11.0.0.2724 .NET version 4.0.30319 Windows version 8.7 Pro Thank you.