realm-swift: Crash happens: Multiple sync agents attempted to join the same session

Goals

Realm Sync normally

Actual Results

Very often crash with this error

terminating with uncaught exception of type realm::MultipleSyncAgents: 
Multiple sync agents attempted to join the same session

UNITO-UNDERSCORE!18-45-22!

UNITO-UNDERSCORE!18-45-33!

libc++abi.dylib: terminating with uncaught exception of type realm::MultipleSyncAgents: Multiple sync agents attempted to join the same session
Exception backtrace:
0   Realm                               0x0000000113de1b78 _ZN5realm2DB7do_openERKNSt3__112basic_stringIcNS1_11char_traitsIcEENS1_9allocatorIcEEEEbbNS_9DBOptionsE + 6620
1   Realm                               0x0000000113de3870 _ZN5realm2DB4openERNS_11ReplicationENS_9DBOptionsE + 244
2   Realm                               0x0000000113de8358 _ZN5realm2DB6createERNS_11ReplicationENS_9DBOptionsE + 392
3   Realm                               0x0000000113b9fde8 _ZN5realm5_impl21ClientFileAccessCache4Slot4openEv + 620
4   Realm                               0x0000000113bef6fc _ZN12_GLOBAL__N_111SessionImpl12access_realmEv + 28
5   Realm                               0x0000000113baa780 _ZN5realm5_impl14ClientImplBase7Session8activateEv + 604
6   Realm                               0x0000000113baa41c _ZN5realm5_impl14ClientImplBase10Connection16activate_sessionENSt3__110unique_ptrINS1_7SessionENS3_14default_deleteIS5_EEEE + 244
7   Realm                               0x0000000113bebd28 _ZN5realm4util7network7Trigger8ExecOperIZN12_GLOBAL__N_110ClientImplC1ENS_4sync6Client6ConfigEEUlvE_E19recycle_and_executeEv + 2104
8   Realm                               0x0000000113cb0bb8 _ZN5realm4util7network7Service4Impl3runEv + 404
9   Realm                               0x0000000113be4fb0 _ZN5realm4sync6Client3runEv + 36
10  Realm                               0x0000000113b000f0 _ZZN5realm5_impl10SyncClientC1ENSt3__110unique_ptrINS_4util6LoggerENS2_14default_deleteIS5_EEEERKNS_16SyncClientConfigENS2_10shared_ptrIKNS_11SyncManagerEEEENKUlvE0_clEv + 232
11  Realm                               0x0000000113afffc0 _ZNSt3__1L8__invokeIZN5realm5_impl10SyncClientC1ENS_10unique_ptrINS1_4util6LoggerENS_14default_deleteIS6_EEEERKNS1_16SyncClientConfigENS_10shared_ptrIKNS1_11SyncManagerEEEEUlvE0_JEEEDTclclsr3std3__1E7forwardIT_Efp_Espclsr3std3__1E7forwardIT0_Efp0_EEEOSI_DpOSJ_ + 28
12  Realm                               0x0000000113afff20 _ZNSt3__1L16__thread_executeINS_10unique_ptrINS_15__thread_structENS_14default_deleteIS2_EEEEZN5realm5_impl10SyncClientC1ENS1_INS6_4util6LoggerENS3_ISA_EEEERKNS6_16SyncClientConfigENS_10shared_ptrIKNS6_11SyncManagerEEEEUlvE0_JEJEEEvRNS_5tupleIJT_T0_DpT1_EEENS_15__tuple_indicesIJXspT2_EEEE + 32
13  Realm                               0x0000000113aff64c _ZNSt3__1L14__thread_proxyINS_5tupleIJNS_10unique_ptrINS_15__thread_structENS_14default_deleteIS3_EEEEZN5realm5_impl10SyncClientC1ENS2_INS7_4util6LoggerENS4_ISB_EEEERKNS7_16SyncClientConfigENS_10shared_ptrIKNS7_11SyncManagerEEEEUlvE0_EEEEEPvSN_ + 116
14  libsystem_pthread.dylib             0x00000001f396ab40 _pthread_start + 320
15  libsystem_pthread.dylib             0x00000001f3973768 thread_start + 8

Code Sample

    public static func writeAsync<T: Object>(obj: T) {
        guard let config = realmConfig else { return }
        realmQueue.async {
            autoreleasepool {
                do {
                    let realm = try? Realm(configuration: config)
                    try realm?.write {
                        realm?.add(obj)
                    }
                }
                catch {
                    print("writeAsync error: \(error.localizedDescription)")
                }
            }
        }
    }

Is there any chance that the mongoDB Sync doesn’t cover the realm object writing and sync at the same times?

Version of Realm and Tooling

Realm framework version: 10.2.0

Xcode version: 12.2

iOS/OSX version: iOS 14.2.1