corrupted prefab in Unity 2021.2.7

some day.
i downloaded "com.unity.entites" from packagemanager.
and i got some problems what i can't explain.

unity editor crashed.
and some prefabs in my project were corrupt.

missing script.
missing prefabs.


i removed "com.unity.entites".
and then
i fixed corrupt prefabs for several days.
i continues to keep working for a while.

but the problems occurred again.

i rollback previous commit.
and i wanted to find the solution.

i thought this is from Unity Editor 2021.2.7(mac sillicon)
so i changed Unity from 2021.2.7 to 2021.2.4 (mac sillicon).





and the following error log occurred.
maybe importing assets has problem.






error log
=============
Problem detected while importing the Prefab file: 'Assets/Stuff/Prefab/Play/Units/Users/user7.prefab'.

The file might be corrupt or have missing nested Prefabs. See details below.

Errors:

Prefab instance problem: gunSub (Missing Prefab with guid: 917afd1095f724af88b3be32ce8edd72)

Prefab instance problem: gunMain (Missing Prefab with guid: b7135570c12c7472ba081aabd706f782)

Prefab instance problem: fxLightBlink (1) (Missing Prefab with guid: 2b4df95143b2248929ead20fff0b71a4). 3 instances are missing the same Prefab

Prefab instance problem: funcUserSpaceship (Missing Prefab with guid: 29514732fe5e64528a54a31a3646c0d0)



#0 GetStacktrace(int)

#1 DebugStringToFile(DebugStringToFileData const&)

#2 ErrorsAndWarningsCapture::LogAsOneMessage(core::basic_string<char, core::StringStorageDefault<char> > const&, int) const

#3 PrefabImporter::GenerateAssetData(AssetImportContext&)

#4 ImportToObjects(core::basic_string<char, core::StringStorageDefault<char> > const&, core::hash_map<AssetDatabase::ImporterID, ImporterInfo, core::hash<AssetDatabase::ImporterID>, std::__1::equal_to<AssetDatabase::ImporterID> > const&, dynamic_array<PostprocessorInfo, 0ul> const&, AssetResolveTracker const&, ImportAssetInputs const&, ImportAssetOutputs&, IImportProgress*)

#5 ImportAsset(core::hash_map<AssetDatabase::ImporterID, ImporterInfo, core::hash<AssetDatabase::ImporterID>, std::__1::equal_to<AssetDatabase::ImporterID> > const&, dynamic_array<PostprocessorInfo, 0ul> const&, AssetResolveTracker const&, ImportAssetInputs const&, ImportAssetOutputs&, IImportProgress*)

#6 ImportAssetWithAutoReleasePool(core::hash_map<AssetDatabase::ImporterID, ImporterInfo, core::hash<AssetDatabase::ImporterID>, std::__1::equal_to<AssetDatabase::ImporterID> > const&, dynamic_array<PostprocessorInfo, 0ul> const&, AssetResolveTracker const&, ImportAssetInputs const&, ImportAssetOutputs&, IImportProgress*)

#7 AssetImportWorker::Import(AssetResolver&, WorkerImportPayload const&, WorkerImportResponse&, IImportProgress*, bool*)

#8 AssetImportManager::ImportInProcess(AssetResolver&, ArtifactKey const&, AssetImportParameters const&, AssetDatabase::ArtifactID&, IImportProgress*, core::hash_set<core::basic_string<char, core::StringStorageDefault<char> >, core::hash<core::basic_string<char, core::StringStorageDefault<char> > >, std::__1::equal_to<core::basic_string<char, core::StringStorageDefault<char> > > >&, CrashedAssetImportsDatabase&)

#9 AssetImportManager::Import(core::hash_map<AssetDatabase::ImporterID, ImporterInfo, core::hash<AssetDatabase::ImporterID>, std::__1::equal_to<AssetDatabase::ImporterID> > const&, dynamic_array<PostprocessorInfo, 0ul> const&, AssetResolver&, CategorizedAssets&, IImportProgress*, core::hash_set<UnityGUID, core::hash<UnityGUID>, std::__1::equal_to<UnityGUID> > const&, LoadedImportedAssetsSnapshot*, LoadedSourceAssetsSnapshot*, core::hash_set<core::basic_string<char, core::StringStorageDefault<char> >, core::hash<core::basic_string<char, core::StringStorageDefault<char> > >, std::__1::equal_to<core::basic_string<char, core::StringStorageDefault<char> > > >&, CrashedAssetImportsDatabase&, bool, OnDemandScheduler&)

#10 RefreshInternalV2(AssetDatabase::UpdateAssetOptions, ScanFilter const&, InternalRefreshFlagsV2)

#11 StopAssetImportingV2Internal(AssetDatabase::UpdateAssetOptions, InternalRefreshFlagsV2, ScanFilter const*, char const*)

#12 RefreshV2(AssetDatabase::UpdateAssetOptions)

#13 VerifyAssetsForBuildTargetV2(bool, AssetDatabase::CancelBehaviour, bool)

#14 AssetDatabase::VerifyAssetsForBuildTarget(bool, AssetDatabase::CancelBehaviour, AssetDatabase::SkipProcessingBehaviour, bool)

#15 ColorSpaceLiveSwitch(bool)

#16 PlayerSettings::SyncCurrentColorSpace(bool)

#17 CheckPlayerSettingsChanged(core::hash_set<UnityGUID, core::hash<UnityGUID>, std::__1::equal_to<UnityGUID> > const&, core::hash_set<UnityGUID, core::hash<UnityGUID>, std::__1::equal_to<UnityGUID> > const&, core::hash_set<UnityGUID, core::hash<UnityGUID>, std::__1::equal_to<UnityGUID> > const&, std::__1::map<UnityGUID, core::basic_string<char, core::StringStorageDefault<char> >, std::__1::less<UnityGUID>, std::__1::allocator<std::__1:air<UnityGUID const, core::basic_string<char, core::StringStorageDefault<char> > > > > const&, AssetDatabase::UpdateAssetOptions)

#18 Postprocess(core::hash_set<UnityGUID, core::hash<UnityGUID>, std::__1::equal_to<UnityGUID> > const&, core::hash_set<UnityGUID, core::hash<UnityGUID>, std::__1::equal_to<UnityGUID> > const&, core::hash_set<UnityGUID, core::hash<UnityGUID>, std::__1::equal_to<UnityGUID> > const&, std::__1::map<UnityGUID, core::basic_string<char, core::StringStorageDefault<char> >, std::__1::less<UnityGUID>, std::__1::allocator<std::__1:air<UnityGUID const, core::basic_string<char, core::StringStorageDefault<char> > > > > const&)

#19 StopAssetImportingV2Internal(AssetDatabase::UpdateAssetOptions, InternalRefreshFlagsV2, ScanFilter const*, char const*)

#20 InitialRefreshV2(bool)

#21 Application::InitializeProject()

#22 -[EditorApplication applicationDidFinishLaunching:]

#23 __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__

#24 ___CFXRegistrationPost_block_invoke

#25 _CFXRegistrationPost

#26 _CFXNotificationPost

#27 -[NSNotificationCenter postNotificationNamebject:userInfo:]

#28 -[NSApplication _postDidFinishNotification]

#29 -[NSApplication _sendFinishLaunchingNotification]

#30 -[NSApplication(NSAppleEventHandling) _handleAEOpenEvent:]

#31 -[NSApplication(NSAppleEventHandling) _handleCoreEvent:withReplyEvent:]

#32 -[NSAppleEventManager dispatchRawAppleEvent:withRawReply:handlerRefCon:]

#33 _NSAppleEventManagerGenericHandler

#34 _AppleEventsCheckInAppWithBlock

#35 _AppleEventsCheckInAppWithBlock

#36 aeProcessAppleEvent

#37 AEProcessAppleEvent

#38 _DPSNextEvent

#39 -[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:]

#40 -[NSApplication run]

#41 NSApplicationMain

#42 EditorMain(int, char const**)

#43 main

#44 ???