When moving a stack consisting of a master photo and one or more virtual copies (should be a common case) from one folder to another (within LR), the stack becomes partially unstacked so that the master photo is no longer part of the stack (but the virtual copies are still grouped into a stack).It does not happen if the stacks are collapsed or the stack consists of master photos only (that are all moved together).Try the following to reproduce:1. Prepare a folder with 1 master photo2. Make two virtual copies. There are now 3 photos in one stack.3. Make sure that the stack is expanded4. Select the master photo or all 3 photos (does not seem to matter)5. Drag them to another, empty folder.6. Select the other folderExpected result: All 3 photos are still grouped into a stack.Actual result: The master photo is no longer in a stack, only the two virtual copies are.When only one virtual copy is used (1 master photo + 1 stacked virtual copy is moved), the stack disappears completely.The problem seems to appear consistently for any number of moved stacks and number of virtual copies in each stack: After the move, the master photos are no longer part of their respective previous stacks.LR 4.1 final 64 Bit Win7.