Try with no other mods installed, neither of the compatibility bridge plugins installed, making sure the included server mod is installed.
Indeed tested. Found a more specific issue. The NCSTAR (dogshit futuristic) scope is the one that hates it.
Errors start to pop up when I swap to the secondary sight in the hideout. To confirm, I tried the same with the Schmidt&Bender 8x and it has no issue. I have picked up the HAMR with a Leupold to test that too but it has no issue.
Here is the updated error. Could be related. Hope it helps!
[Exception] : IndexOutOfRangeException: Index was outside the bounds of the array.
EFT.InventoryLogic.SightComponent.GetCurrentOpticZoom () (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
FOVFix.method_20Patch.PatchPostfix (EFT.Animations.ProceduralWeaponAnimation& __instance) (at <2c71f0456e434e7fa9ffd40078b3b8cb>:0)
(wrapper dynamic-method) EFT.Animations.ProceduralWeaponAnimation.DMD<EFT.Animations.ProceduralWeaponAnimation::method_20>(EFT.Animations.ProceduralWeaponAnimation)
(wrapper dynamic-method) EFT.Animations.ProceduralWeaponAnimation.DMD<EFT.Animations.ProceduralWeaponAnimation::set_IsAiming>(EFT.Animations.ProceduralWeaponAnimation,bool)
GClass1596.SetAiming (System.Boolean aim) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
EFT.Player+FirearmController.set_IsAiming (System.Boolean value) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
EFT.Player+FirearmController+GClass1550.SetAiming (System.Boolean isAiming) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
EFT.Player+FirearmController.SetAim (System.Boolean value) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
Class1384.TranslateCommand (EFT.InputSystem.ECommand command) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
EFT.PlayerOwner.TranslateCommand (EFT.InputSystem.ECommand command) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
EFT.GamePlayerOwner.TranslateCommand (EFT.InputSystem.ECommand command) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
EFT.HideoutPlayerOwner.TranslateCommand (EFT.InputSystem.ECommand command) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
EFT.InputSystem.InputNode.TranslateInput (System.Collections.Generic.List`1[T] commands, System.Single[]& axes, EFT.InputSystem.ECursorResult& shouldLockCursor) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
EFT.InputSystem.InputNodeAbstract.TranslateInput (System.Collections.Generic.List`1[T] commands, System.Single[]& axes, EFT.InputSystem.ECursorResult& shouldLockCursor) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
EFT.InputSystem.InputManager.method_3 (System.Collections.Generic.List`1[T] commandsList, System.Single[] axesList) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
EFT.InputSystem.InputManager.method_2 () (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
EFT.InputSystem.InputManager.Update () (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
UnityEngine.DebugLogHandler:LogException(Exception, Object)
Class311:UnityEngine.ILogHandler.LogException(Exception, Object)
UnityEngine.Debug:CallOverridenDebugHandler(Exception, Object)
[Exception] : IndexOutOfRangeException: Index was outside the bounds of the array.
EFT.InventoryLogic.SightComponent.GetCurrentOpticZoom () (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
FOVFix.method_20Patch.PatchPostfix (EFT.Animations.ProceduralWeaponAnimation& __instance) (at <2c71f0456e434e7fa9ffd40078b3b8cb>:0)
(wrapper dynamic-method) EFT.Animations.ProceduralWeaponAnimation.DMD<EFT.Animations.ProceduralWeaponAnimation::method_20>(EFT.Animations.ProceduralWeaponAnimation)
(wrapper dynamic-method) EFT.Animations.ProceduralWeaponAnimation.DMD<EFT.Animations.ProceduralWeaponAnimation::method_22>(EFT.Animations.ProceduralWeaponAnimation,int)
GClass2921`1[T].method_0 (T newState) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
BindableState[T].set_Value (T value) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
(wrapper dynamic-method) EFT.Player+FirearmController.DMD<EFT.Player+FirearmController::ChangeAimingMode>(EFT.Player/FirearmController)
Class1384.TranslateCommand (EFT.InputSystem.ECommand command) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
EFT.PlayerOwner.TranslateCommand (EFT.InputSystem.ECommand command) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
EFT.GamePlayerOwner.TranslateCommand (EFT.InputSystem.ECommand command) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
EFT.HideoutPlayerOwner.TranslateCommand (EFT.InputSystem.ECommand command) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
EFT.InputSystem.InputNode.TranslateInput (System.Collections.Generic.List`1[T] commands, System.Single[]& axes, EFT.InputSystem.ECursorResult& shouldLockCursor) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
EFT.InputSystem.InputNodeAbstract.TranslateInput (System.Collections.Generic.List`1[T] commands, System.Single[]& axes, EFT.InputSystem.ECursorResult& shouldLockCursor) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
EFT.InputSystem.InputManager.method_3 (System.Collections.Generic.List`1[T] commandsList, System.Single[] axesList) (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
EFT.InputSystem.InputManager.method_2 () (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
EFT.InputSystem.InputManager.Update () (at <89c8c8aab2ad44ff89f90df9bc38d688>:0)
UnityEngine.DebugLogHandler:LogException(Exception, Object)
Class311:UnityEngine.ILogHandler.LogException(Exception, Object)
UnityEngine.Debug:CallOverridenDebugHandler(Exception, Object)