The stack shows 1070 repeated frames of:

• StructElementObject.ProcessChildPrimitive(...)
• StructElementObject.CopyPropertiesTo(...)

The StructureTree import is traversing a cyclic StructElement graph (or equivalent re-entrant child chain) without a recursion guard.

During this recursion, indirect object resolution repeatedly re-enters the same compressed object:

• reference.ObjectNumber = 554
• context.CurrentIndirectReference.ObjectNumber = 554
• TryGetIndirectObject(554, ...) == false at re-entry