The video demonstrates the problem. NavLock gets out of step after swapping sides in a synchronise session. As shown, everything is fine until the swap sides button is clicked. After that, any movement up/down the folder structure on either pane generates an out of sync message. Switching NavLock off and on again fixes things until the swap button is clicked again. This is with Opus v10.5.0.3 but it has been around for a while - I just never got around to reporting it.
See video here.