I solved this problem by installing sole FBX Python SDK 2020.0.1 package from https://www.autodesk.com/developer-network/platform-technologies/fbx-sdk-2020-0 and it solved the issue. All other packages that I installed: com.autodesk.fbxpythonbindings202001 com.autodesk.fbxsdkext202001 And after I uninstalled all unused packages with pkgutil I still can import FBX models.

Now XCBBuildService quit unexpectedly. keeps stopping: System Integrity Protection: enabled Crashed Thread: 5 Dispatch queue: XCBBuildSystem.BuildManager.buildQueue Exception Type: EXC_BREAKPOINT (SIGTRAP) Exception Codes: 0x0000000000000001, 0x0000000102c41018 Exception Note: EXC_CORPSE_NOTIFY Termination Reason: Namespace SIGNAL, Code 5 Trace/BPT trap: 5 Terminating Process: exc handler [36741] Thread 0:: Dispatch queue: XCBBuildService.ServiceHostConnection.receiveQueue 0 libsystem_kernel.dylib 0x19ec27634 read + 8 1 XCBServiceCore 0x102bb7d90 closure #1 in ServiceHostConnection.resume() + 96 2 XCBServiceCore 0x102bb90f4 thunk for @escaping @callee_guaranteed () -> () + 28 3 libdispatch.dylib 0x19ea9e5f0 _dispatch_call_block_and_release + 32 4 libdispatch.dylib 0x19eaa01b4 _dispatch_client_callout + 20 5 libdispatch.dylib 0x19eaa78a8 _dispatch_lane_serial_drain + 668 6 libdispatch.dylib 0x19eaa8404 _dispatch_lane_invoke + 392 7 libdispatch.dylib 0x19eab2c98 _dispatch_workloop_worker_thread + 648 8 libsystem_pthread.dylib 0x19ec60360 _pthread_wqthread + 288 9 libsystem_pthread.dylib 0x19ec5f080 start_wqthread + 8 Thread 5 Crashed:: Dispatch queue: XCBBuildSystem.BuildManager.buildQueue 0 XCBBuildSystem 0x102c41018 DependencyCycleFormatter.filteredCycleOutput() + 3428 1 XCBBuildSystem 0x102c40c70 DependencyCycleFormatter.filteredCycleOutput() + 2492 2 XCBBuildSystem 0x102c3fc2c DependencyCycleFormatter.formattedMessage() + 56 3 XCBBuildSystem 0x102c53530 OperationSystemAdaptor.cycleDetected(rules:) + 272 4 XCBBuildSystem 0x102c53dc0 protocol witness for BuildSystemDelegate.cycleDetected(rules:) in conformance OperationSystemAdaptor + 20 5 llbuild 0x10373e678 0x103724000 + 108152 6 llbuild 0x10372d0a8 (anonymous namespace)::CAPIBuildSystemFrontendDelegate::cycleDetected(std::__1::vector<llbuild::core::Rule*, std::__1::allocator<llbuild::core::Rule*> > const&) + 52 7 llbuild 0x1037b1cec (anonymous namespace)::BuildEngineImpl::executeTasks(llbuild::core::KeyType const&) + 8364 8 llbuild 0x1037ad918 llbuild::core::BuildEngine::build(llbuild::core::KeyType const&) + 568 9 llbuild 0x1037c486c (anonymous namespace)::BuildSystemImpl::build(llbuild::buildsystem::BuildKey) + 164 10 llbuild 0x1037c47a8 llbuild::buildsystem::BuildSystem::build(llbuild::buildsystem::BuildKey) + 48 11 llbuild 0x1037bad68 llbuild::buildsystem::BuildSystemFrontend::buildNode(llvm::StringRef) + 104 12 llbuild 0x10373ea48 0x103724000 + 109128 13 XCBBuildSystem 0x102c47c70 BuildOperation.build() + 8080 14 XCBBuildSystem 0x102c60c9c closure #2 in BuildManager.startBuild(_:) + 60 15 XCBBuildSystem 0x102c602a0 thunk for @escaping @callee_guaranteed () -> () + 28 16 libdispatch.dylib 0x19eaaefb4 _dispatch_block_async_invoke2 + 148 17 libdispatch.dylib 0x19eaa01b4 _dispatch_client_callout + 20 18 libdispatch.dylib 0x19eaa3670 _dispatch_continuation_pop + 500 19 libdispatch.dylib 0x19eaa2cdc _dispatch_async_redirect_invoke + 584 20 libdispatch.dylib 0x19eab18e8 _dispatch_root_queue_drain + 396 21 libdispatch.dylib 0x19eab2104 _dispatch_worker_thread2 + 164 22 libsystem_pthread.dylib 0x19ec60324 _pthread_wqthread + 228 23 libsystem_pthread.dylib 0x19ec5f080 start_wqthread + 8 Binary Images: 0x19ec25000 - 0x19ec5cfff libsystem_kernel.dylib (*) <03f48dc5-caa7-3678-af61-1a3c7fa8b06e> /usr/lib/system/libsystem_kernel.dylib 0x102bb0000 - 0x102bbffff com.apple.dt.XCBServiceCore (13.4.1) <8d9dea8c-f0a1-3a95-8cbe-4672b2e3af7a> /Applications/Xcode.app/Contents/SharedFrameworks/XCBuild.framework/Versions/A/PlugIns/XCBBuildService.bundle/Contents/Frameworks/XCBServiceCore.framework/Versions/A/XCBServiceCore 0x19ea9c000 - 0x19eae2fff libdispatch.dylib (*) <f9300d47-d3db-3349-8a6d-acb68cd9983b> /usr/lib/system/libdispatch.dylib 0x19ec5d000 - 0x19ec69fff libsystem_pthread.dylib (*) <42166a2c-89a9-3c38-a215-f028544cea23> /usr/lib/system/libsystem_pthread.dylib 0x102c3c000 - 0x102c6bfff com.apple.dt.XCBBuildSystem (13.4.1) <a160309b-c87c-396a-8a43-9ab52151ccfb> /Applications/Xcode.app/Contents/SharedFrameworks/XCBuild.framework/Versions/A/PlugIns/XCBBuildService.bundle/Contents/Frameworks/XCBBuildSystem.framework/Versions/A/XCBBuildSystem

And after 1st build Xcode refuses to build with the following error Build service could not create build operation: unknown error while handling message: unknownSession

sure, I tried

AppStore doesn't accept apps built with Xcode 12 anymore.

Sorry, I posted in the wrong thread, but still I got the same issue with the latest Xcode.

I fixed it by running: defaults delete com.apple.dt.Xcode defaults delete com.apple.dt.xcodebuild defaults delete apple.preferences.extensions.XcodeSourceEditor

When trying to re-build: Build service could not create build operation: unknown error while handling message: unknownSession

2022-06-14 19:06:41.060 *** Error: /Applications/Xcode.app/Contents/Developer/usr/bin/bitcode-build-tool (2): bitcode-build-tool internal error Traceback (most recent call last):   File "/Applications/Xcode.app/Contents/Developer/usr/bin/bitcode-build-tool", line 10, in <module>     bitcode_build_tool_main(sys.argv)   File "/Applications/Xcode.app/Contents/Developer/usr/bin/../lib/bitcode_build_tool/main.py", line 65, in main     env.initState(args)   File "/Applications/Xcode.app/Contents/Developer/usr/bin/../lib/bitcode_build_tool/buildenv.py", line 159, in initState     self.logger.debug("SDK path: {}".format(self.sdk)) AttributeError: 'BuildEnvironment' object has no attribute 'sdk' same error. When I just call altool there is no any erroneous output.

I solved it with a temporary solution by utilizing Xcode 13.2.1.