The references C67D, C5D1, C5CC, C63B@open cities skyrim.esp are all associated with Vittoria Vici's wedding, yet they are enabled at all time. This causes them to lie scattered on the ground, since the objects they are placed upon are disabled. To fix this, you need to assign DB05WeddingEnableMarker as an enable parent to them.
The corresponding Vanilla objects are not subject to this bug, or at least not with USSEP installed.