It looks like you are already aware of this crash judging by the added info that is output regarding the crew in the log.
03/24/2018 19:49:01 | Game mode is: TeamVersusGameModeManager
03/24/2018 19:49:05 | _crew.Count: 515
03/24/2018 19:49:05 | _nextCrewmanToUpdate: 254
03/24/2018 19:49:05 | separatingTime: 354.805729052847
03/24/2018 19:49:05 | index: -12
03/24/2018 19:49:05 | list contains removed crewman: True
03/24/2018 19:49:05 | Memory usage at time of crash: 2,072,186,880
03/24/2018 19:49:05 | Application state stack at time of crash:
03/24/2018 19:49:05 | Cosmoteer.Game.GameRoot
03/24/2018 19:49:05 | Cosmoteer.Gui.TitleScreen
03/24/2018 19:49:05 | FPS at time of crash: 24.51332
03/24/2018 19:49:05 | Running processes at time of crash: ApplicationFrameHost, armsvc, audiodg, bcastdvr, BrcmSetSecurity, Calculator, chrome, conhost, Cosmoteer, csrss, ctfmon, dasHost, DbxSvc, dllhost, DropboxUpdate, dwm, explorer, fontdrvhost, HeciServer, Idle, igfxCUIService, igfxEM, igfxext, igfxHK, igfxTray, IntelMeFWService, Jhi_service, LMS, LockApp, lsass, Memory Compression, Microsoft.Photos, MSASCuiL, MsMpEng, NetworkClient, NFCConnectionUtility, NisSrv, OfficeClickToRun, perfmon, PresentationFontCache, RAVBg64, RtkAudioService64, RuntimeBroker, SearchFilterHost, SearchIndexer, SearchProtocolHost, SearchUI, SecurityHealthService, services, SettingSyncHost, ShellExperienceHost, sihost, smss, spoolsv, SUSSoundProxy, svchost, SynTPEnh, SynTPEnhService, SynTPHelper, System, SystemSettings, TabTip, TabTip32, taskhostw, Taskmgr, VAIO Clip, VAIOUpdt, VESGfxMgr, VESMgr, VESMgrSub, vim, vpnagent, VUAgent, wininit, winlogon, wlanext, WUDFHost,
03/24/2018 19:49:05 | System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
03/24/2018 19:49:05 | Parameter name: index
03/24/2018 19:49:05 | at System.ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument argument, ExceptionResource resource)
03/24/2018 19:49:05 | at System.Collections.Generic.List`1.RemoveAt(Int32 index)
03/24/2018 19:49:05 | at Cosmoteer.Ships.Crew.CrewManager.RemoveCrewmanFromUpdateList(Crewman c) in C:\Users\Walt\Documents\Code\Cosmoteer\Source\Ships\Crew\CrewManager.cs:line 469
03/24/2018 19:49:05 | at Cosmoteer.Ships.Crew.CrewManager.RemoveCrewman(Crewman crewman, Boolean killed) in C:\Users\Walt\Documents\Code\Cosmoteer\Source\Ships\Crew\CrewManager.cs:line 244
03/24/2018 19:49:05 | at Cosmoteer.Ships.Crew.Crewman.Kill(DeathCause cause) in C:\Users\Walt\Documents\Code\Cosmoteer\Source\Ships\Crew\Crewman.cs:line 447
03/24/2018 19:49:05 | at Cosmoteer.Ships.Parts.PartsManager.RemovePart(Part part, Boolean killCrew, Boolean moveCrew, Boolean destroyed, Boolean removeDoors) in C:\Users\Walt\Documents\Code\Cosmoteer\Source\Ships\Parts\PartsManager.cs:line 231
03/24/2018 19:49:05 | at Cosmoteer.Ships.Parts.PartsManager.OnPartDestroyed(Object sender, EventArgs e) in C:\Users\Walt\Documents\Code\Cosmoteer\Source\Ships\Parts\PartsManager.cs:line 481
03/24/2018 19:49:05 | at System.EventHandler`1.Invoke(Object sender, TEventArgs e)
03/24/2018 19:49:05 | at Cosmoteer.Ships.Parts.Part.OnHealthChanged(Int32 oldValue, Int32 newValue) in C:\Users\Walt\Documents\Code\Cosmoteer\Source\Ships\Parts\Part.cs:line 638
03/24/2018 19:49:05 | at Cosmoteer.Ships.Parts.Part.set_Health(Int32 value) in C:\Users\Walt\Documents\Code\Cosmoteer\Source\Ships\Parts\Part.cs:line 122
03/24/2018 19:49:05 | at Cosmoteer.Ships.Parts.Part.OnHit(Int32 damage) in C:\Users\Walt\Documents\Code\Cosmoteer\Source\Ships\Parts\Part.cs:line 335
03/24/2018 19:49:05 | at Cosmoteer.Simulation.HitEffects.PartAreaDamageEffectRules.DoDamageAgainstType(Ship ship, Ship sourceShip, Vector2D loc, Int32 damagePerTile, Single radius, Single falloff, Single dmgFactor, HealthType healthType) in C:\Users\Walt\Documents\Code\Cosmoteer\Source\Simulation\HitEffects\PartAreaDamageEffectRules.cs:line 115
03/24/2018 19:49:05 | at Cosmoteer.Simulation.HitEffects.PartAreaDamageEffectRules.<DoEffect>d__8.MoveNext() in C:\Users\Walt\Documents\Code\Cosmoteer\Source\Simulation\HitEffects\PartAreaDamageEffectRules.cs:line 62
03/24/2018 19:49:05 | --- End of stack trace from previous location where exception was thrown ---
03/24/2018 19:49:05 | at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
03/24/2018 19:49:05 | at Halfling.Application.QueueingSyncContext.HandleQueue() in C:\Users\Walt\Documents\Code\Cosmoteer\Halfling\HalflingCore\Application\QueueingSyncContext.cs:line 42
03/24/2018 19:49:05 | at Halfling.Application.Director.<GetRunIterator>d__83.MoveNext() in C:\Users\Walt\Documents\Code\Cosmoteer\Halfling\HalflingCore\Application\Director.cs:line 320
03/24/2018 19:49:05 | at Halfling.Application.Bases.GenericApp.<ApplicationMainIterator>d__42.MoveNext() in C:\Users\Walt\Documents\Code\Cosmoteer\Halfling\HalflingCore\Application\Bases\GenericApp.cs:line 249
03/24/2018 19:49:05 | at Halfling.Windows.D3D11.D3D11Window.RunGameLoop(String[] args, IEnumerable`1 iterator) in C:\Users\Walt\Documents\Code\Cosmoteer\Halfling\HalflingPlatformWDX\Windows\D3D11\D3D11Window.cs:line 883
03/24/2018 19:49:05 | at Halfling.Application.Bases.GenericApp.ApplicationMain(String[] args) in C:\Users\Walt\Documents\Code\Cosmoteer\Halfling\HalflingCore\Application\Bases\GenericApp.cs:line 165
03/24/2018 19:49:05 | at Cosmoteer.GameApp.Main(String[] args) in C:\Users\Walt\Documents\Code\Cosmoteer\Source\GameApp.cs:line 119
