NullReferenceException at LODComponent.ChangeLODSolved

a bunch of red text appears in the top left of player's screens and they are getting force disconnected when it happens. i can reproduce the error by flying a mini heli in a certain area of the map. any help?

[0.6s] Processing World
UnityEngine.Logger:Log(LogType, Object)
UnityEngine.Debug:Log(Object)
TimerSwitch:get_HasMenuOptions()
<InitCoroutine>d__14:MoveNext()
UnityEngine.SetupCoroutine:InvokeMoveNext(IEnumerator, IntPtr)
Unloading 0 Unused Serialized files (Serialized files now loaded: 58)
Unloading 14 unused Assets to reduce memory usage. Loaded Objects now: 1924697.
Total: 1380.551100 ms (FindLiveObjects: 137.587500 ms CreateObjectMapping: 128.710600 ms MarkObjects: 1112.278800 ms DeleteObjects: 1.973600 ms)
Destroyed 947 map networkables
UnityEngine.Logger:Log(LogType, Object)
UnityEngine.Debug:Log(Object)
Client:DestroyNetworkables()
<DoClientConnected>d__34:MoveNext()
UnityEngine.SetupCoroutine:InvokeMoveNext(IEnumerator, IntPtr)
at LODComponent.ChangeLOD () [0x00000] in <00000000000000000000000000000000>:0
at LODCell.ChangeLOD () [0x00000] in <00000000000000000000000000000000>:0
at LODGrid+<UpdateCoroutine>d__27.MoveNext () [0x00000] in <00000000000000000000000000000000>:0
at UnityEngine.SetupCoroutine.InvokeMoveNext (System.Collections.IEnumerator enumerator, System.IntPtr returnValueAddress) [0x00000] in <00000000000000000000000000000000>:0
(Filename: currently not available on il2cpp Line: -1)

Fixed with clean server install 
Locked automatically