Thanks Gryphon, here's that information KSP: 1.0.4 Final Frontier causing issues when rescued Kerbals attempt to enter rescue vessel Win 7x64 Mods installed: Final Frontier 0.8.6-1370 ModularFlightIntegrator 1.1.1.0 FAR 0.15.4 PreciseNode 1.1.3 DeadlyReentry 7.2.2 Module Manager 2.6.7 StageRecovery 1.5.7 ScienceAlert 1.8.9 RasterPropMonitor 0.21.2 Kerbal Alarm Clock 3.4.0.0 Chatterer 0.9.6 Trajectories 1.4.3 KAS 0.5.4 KIS 1.2.1 USI Tools 0.4.2 ActiveTextureManagement 5-0 CommunityResourcePack 0.4.3 CommnityTechTree 2.1 ContractConfigurator 1.6.3 ContractPack-RemoteTech 2.0.0 ContractsWindow 5.3 EditorExtensions 2.12 EVE (City Lights & Clouds) Low Res 7-4 Firespitter.dll v7.1.4 ImprovedChaseCamera 1.5.1 KerbalEngineer 1.0.18.0 KerbalJointReinforcement 3.1.4 KSP-AVC 1.1.5.0 NavHud 1.2.1 Docking Port Alignment Indicator 6.2 ProceduralFairings 3.15 ProceduralFairings-ForEverything 0.0.3 QuickExit 1.31 QuickHide 3.02 QuickScroll 1.31 RcsSounds 4.3 RemoteTech 1.6.7 RKE_Joystick 1.2.1 SCANsat 13.4 ScienceAlert Karbonite 0.6.3 Karbonite+ 0.4.1 WaypointManager 2.4.2 WheelSounds 1.2 Reproduction steps: Go on a contract rescue mission with an extra seat for a kerbal to rescue. When attempting to have the rescued kerbal enter your vessel, duplicate bug will occur, leaving one kerbal inside and their exact twin on the outside. Attempting to have twin kerbal enter from an empty module temporarily fixes the bug, but on exit and attempt to reenter, the bug will reoccur. Log: Log file