I catch an interesting issue. Raiders arives in pods and some of the drops happens in the center of my base.

In logs I found something like this.

DropThingsNear failed to find a place to drop David near (248, 0, 1). Dropping on random square instead.
Verse.Log:Warning(String, Boolean)
RimWorld.DropPodUtility:DropThingGroupsNear_NewTmp(IntVec3, Map, List`1, Int32, Boolean, Boolean, Boolean, Boolean, Boolean)
RimWorld.DropPodUtility:DropThingGroupsNear(IntVec3, Map, List`1, Int32, Boolean, Boolean, Boolean, Boolean)
RimWorld.DropPodUtility:DropThingsNear(IntVec3, Map, IEnumerable`1, Int32, Boolean, Boolean, Boolean, Boolean)
RimWorld.PawnsArrivalModeWorkerUtility:DropInDropPodsNearSpawnCenter(IncidentParms, List`1)
RimWorld.PawnsArrivalModeWorker_EdgeDrop:Arrive(List`1, IncidentParms)
Battlemounts.Harmony.IncidentWorker_Raid_TryExecuteWorker:MountAnimals(PawnGroupMakerParms, Boolean, IncidentParms)
RimWorld.IncidentWorker_Raid:DMD<DMD<TryExecuteWorker_Patch0>?833842432::TryExecuteWorker_Patch0>(IncidentWorker_Raid, IncidentParms)
RimWorld.IncidentWorker_RaidEnemy:TryExecuteWorker(IncidentParms)
RimWorld.IncidentWorker:TryExecute(IncidentParms)
RimWorld.Storyteller:TryFire(FiringIncident)
Rimatomics.RimatomicsResearch:IncidentQueueTick()
Rimatomics.RimatomicsResearch:WorldComponentTick()
RimWorld.Planet.WorldComponentUtility:WorldComponentTick(World)
RimWorld.Planet.World:WorldTick()
Verse.TickManager:DMD<DMD<DoSingleTick_Patch1>?1124151936::DoSingleTick_Patch1>(TickManager)
Verse.TickManager:TickManagerUpdate()
Verse.Game:UpdatePlay()
Verse.Root_Play:Update()