Objective-C多线程崩溃问题

问题遇到的现象和发生背景

偶先崩溃，因为启动进入到此页面，大概没启动 APP3-5 次出现崩溃一次，因为多线程原因，具体原因未知，改动之后 bug 解决，为什么能解决也不清楚，请大 佬解惑，
FAMallBindVM 里面是网络请求，请求成功之后会有dispatch_group_leave一一对应

问题相关代码，请勿粘贴截图

dispatch_group_t group = dispatch_group_create();
self.viewModel.disGroup = group;
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
__weak typeof(self) weakSelf = self;

dispatch_group_enter(self.viewModel.disGroup);
dispatch_group_async(self.viewModel.disGroup, queue, ^{
    [FAMallBindVM postBanner:weakSelf.viewModel];
});

dispatch_group_enter(self.viewModel.disGroup);
dispatch_group_async(self.viewModel.disGroup, queue, ^{
    [FAMallBindVM postNews:weakSelf.viewModel];
});

dispatch_group_enter(self.viewModel.disGroup);
dispatch_group_async(self.viewModel.disGroup, queue, ^{
    [FAMallBindVM postCategory:weakSelf.viewModel];
});

dispatch_group_enter(self.viewModel.disGroup);
dispatch_group_async(self.viewModel.disGroup, queue, ^{
    [FAMallBindVM postArticle:weakSelf.viewModel];
});
  
dispatch_group_notify(self.viewModel.disGroup, queue, ^{
    [weakSelf.mainTableView refreshHandle:HJRefresh_end];
});

运行结果及报错内容

唯一不同的是这块代码，我把里面的网络请求内容拿出来了，拿出来之后问题解决
dispatch_group_async(self.viewModel.disGroup, queue, ^{
[FAMallBindVM postCategory:weakSelf.viewModel];
});

我的解答思路和尝试过的方法

此处代码问题解决
dispatch_group_t group = dispatch_group_create();
self.viewModel.disGroup = group;
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_group_enter(self.viewModel.disGroup);
[FAMallBindVM postBanner:self.viewModel];

dispatch_group_enter(self.viewModel.disGroup);
[FAMallBindVM postNews:self.viewModel];

dispatch_group_enter(self.viewModel.disGroup);
[FAMallBindVM postCategory:self.viewModel];

dispatch_group_enter(self.viewModel.disGroup);
[FAMallBindVM postArticle:self.viewModel];
  
__weak typeof(self) weakSelf = self;
dispatch_group_notify(self.viewModel.disGroup, queue, ^{
    [weakSelf.mainTableView refreshHandle:HJRefresh_end];
});

我想要达到的结果

你把崩溃前得日志发给我，我看看错误提示得内容