Slitherine

Happens every time i load this turn, not a once off - 2nd playthrough, first time didn't bother with quest and no grief - no mods enabled.

Quest.cpp:186: void __cdecl gladius::world::quest::Quest::onStageComplete(void): Assertion "completedStages < stages.size()" failed.
ExceptionHandler::unhandledExceptionFilter()
Quest.cpp:186: void __cdecl gladius::world::quest::Quest::onStageComplete(void): Assertion "completedStages < stages.size()" failed.
(0) [0x00007FF901854F69] RaiseException + 0x0000000000000069 (C:\Windows\System32\KERNELBASE.dll)
(1) [0x00007FF8E0C3486D] _CxxThrowException + 0x00000000000000AD (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\VCRUNTIME140.dll)
(2) [0x00007FF6223E2D67] void __cdecl std::_Throw_with_nested<class proxy::core::Exception>(class proxy::core::Exception && __ptr64,struct std::integral_constant<bool,1>) + 0x0000000000000027 (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(3) [0x00007FF6223E35A6] void __cdecl std::throw_with_nested<class proxy::core::Exception>(class proxy::core::Exception && __ptr64) + 0x0000000000000016 (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(4) [0x00007FF6227D81A8] public: void __cdecl gladius::world::quest::Quest::onStageComplete(void) __ptr64 + 0x0000000000000378 (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(5) [0x00007FF6227D9F38] public: void __cdecl gladius::world::quest::Stage::onObjectiveComplete(void) __ptr64 + 0x0000000000000078 (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(6) [0x00007FF62295224C] public: virtual void __cdecl gladius::world::quest::objective::ResearchUpgradeTier::start(void) __ptr64 + 0x000000000000006C (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(7) [0x00007FF6227DA0B9] public: void __cdecl gladius::world::quest::Stage::start(void) __ptr64 + 0x0000000000000089 (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(8) [0x00007FF6227D7F6E] public: void __cdecl gladius::world::quest::Quest::onStageComplete(void) __ptr64 + 0x000000000000013E (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(9) [0x00007FF6227D9F38] public: void __cdecl gladius::world::quest::Stage::onObjectiveComplete(void) __ptr64 + 0x0000000000000078 (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(10) [0x00007FF6226C665C] public: void __cdecl proxy::core::Listeners<class gladius::world::UnitListener>::send<class gladius::world::UnitProducedMessage>(class gladius::world::UnitProducedMessage const & __ptr64) __ptr64 + 0x000000000000011C (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(11) [0x00007FF62292940D] public: virtual void __cdecl gladius::world::action::ProduceUnit::end(void) __ptr64 + 0x00000000000002CD (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(12) [0x00007FF6227AC8B9] public: virtual void __cdecl gladius::world::Actor::process(void) __ptr64 + 0x0000000000000159 (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(13) [0x00007FF622850A3C] public: void __cdecl gladius::world::BuildingGroupManager::process(class gladius::world::Player & __ptr64) __ptr64 + 0x000000000000016C (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(14) [0x00007FF622753971] private: void __cdecl gladius::world::PlayerManager::process(class gladius::world::Player & __ptr64) __ptr64 + 0x0000000000000301 (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(15) [0x00007FF62275358C] public: void __cdecl gladius::world::PlayerManager::nextSubTurn(void) __ptr64 + 0x000000000000051C (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(16) [0x00007FF62273538A] public: void __cdecl gladius::world::World::update(double) __ptr64 + 0x000000000000083A (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(17) [0x00007FF6224104E4] public: virtual void __cdecl gladius::gui::GUI::update(double) __ptr64 + 0x0000000000000044 (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(18) [0x00007FF6224FA3B2] public: void __cdecl proxy::gui::GUI::run(void) __ptr64 + 0x00000000000000F2 (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(19) [0x00007FF62240A187] public: int __cdecl gladius::Game::main(int,char * __ptr64 * __ptr64,char * __ptr64 * __ptr64) __ptr64 + 0x0000000000000017 (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(20) [0x00007FF6223E02BF] main + 0x000000000000003F (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(21) [0x00007FF6229A8B74] __scrt_common_main_seh + 0x000000000000010C (D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe)
(22) [0x00007FF902B87034] BaseThreadInitThunk + 0x0000000000000014 (C:\Windows\System32\KERNEL32.DLL)
(23) [0x00007FF903DE2651] RtlUserThreadStart + 0x0000000000000021 (C:\Windows\SYSTEM32\ntdll.dll)
Modules loaded:
D:\Games\SteamLibrary\steamapps\common\Warhammer 40000 Gladius - Relics of War\Binaries\Windows-x86_64\Gladius.exe

The game crashes on the "chapter V" quest of the adeptus mechanicus faction.
The error occurs when you bring the Sicarian Infiltrator to the place of the destroyed fortress.
Since all the living creatures and non-living creatures are destroyed, an error occurs and the game crashes.

Same here, lets hope this will be solved soon.