Weird behaviour of a deserialized class

I've got a huge XML file that's being deserialized by XmlSerializer in an XSD-generated class structure. Everything used to work just fine, but now a weird thing started happening. Sometimes (50% of runs) a field of a certain object of a class that's deep in the class tree just changes to a certain value of the same field of a different object of the same class. It happens when entering some function, when debugger steps from opening "{" to the first line of code.

I understand that it's stupid question, but maybe someone have any th开发者_运维技巧oughts?

---

We have dozens of thoughts. There can be plenty of reasons. You need to investigate it more precisely. Your self.