Failed to add item because it exists after clear region

[rider11-dev]

I'm using cache both in memory and redis,and I'm trying to reload cache using the following steps:
1.clear region(which is already loaded from app start);
2.add my new cache data;
It works in most cases,but I got a strange thing for "Failed to add item because it exists" sometimes ,
logs are as below:
2020-01-13 16:12:40.2798|TRACE|service:|CacheManager.Core.BaseCacheManager|Clear region: SysRegion.||traceid:|requestid:|GoldDustSyscfgCacheLoader.Load => BaseCacheManager1.ClearRegion => MicrosoftLoggerAdapter.Log
2020-01-13 16:12:40.2798|TRACE|service:|CacheManager.Core.BaseCacheManager|Clear region: SysRegion in handle innerMemoryCache.||traceid:|requestid:|GoldDustSyscfgCacheLoader.Load => BaseCacheManager1.ClearRegion => MicrosoftLoggerAdapter.Log 2020-01-13 16:12:40.2798|TRACE|service:|CacheManager.Core.BaseCacheManager|**Clear region: SysRegion in handle redisCache**.||traceid:|requestid:|GoldDustSyscfgCacheLoader.Load => BaseCacheManager1.ClearRegion => MicrosoftLoggerAdapter.Log
2020-01-13 16:12:40.2849|TRACE|service:|CacheManager.Core.BaseCacheManager|Clear region: SysRegion: notifies backplane [clear region].||traceid:|requestid:|GoldDustSyscfgCacheLoader.Load => BaseCacheManager1.ClearRegion => MicrosoftLoggerAdapter.Log 2020-01-13 16:12:40.2908|TRACE|service:|CacheManager.Core.BaseCacheManager|Add ['SysRegion:c|包装方式_n|1', exp:Default 00:00:00, lastAccess:2020-01-13 08:12:40.289] started.||traceid:|requestid:|CacheManagerHelper.Add => BaseCacheManager1.AddInternal => MicrosoftLoggerAdapter.Log
2020-01-13 16:12:40.2930|DEBUG|service:|CacheManager.Redis.RedisCacheHandle|DB 3 | Failed to add item ['SysRegion:c|包装方式_n|1', exp:Absolute 7.00:00:00, lastAccess:2020-01-13 08:12:40.289] because it exists.||traceid:|requestid:|RetryHelper.Retry => RedisCacheHandle1.Set => MicrosoftLoggerAdapter.Log 2020-01-13 16:12:40.2941|TRACE|service:|CacheManager.Core.BaseCacheManager|Evict [SysRegion:c|包装方式_n|1] from other handles excluding handle '1'.||traceid:|requestid:|BaseCacheManager1.AddInternal => BaseCacheManager1.EvictFromOtherHandles => MicrosoftLoggerAdapter.Log 2020-01-13 16:12:40.2941|DEBUG|service:|CacheManager.Core.BaseCacheManager|Evicting 'SysRegion:c|包装方式_n|1' from handle 'innerMemoryCache'.||traceid:|requestid:|BaseCacheManager1.EvictFromOtherHandles => BaseCacheManager1.EvictFromHandle => MicrosoftLoggerAdapter.Log 2020-01-13 16:12:40.2941|TRACE|service:|CacheManager.Core.BaseCacheManager|Add ['SysRegion:c|包装方式_n|2', exp:Default 00:00:00, lastAccess:2020-01-13 08:12:40.294] started.||traceid:|requestid:|CacheManagerHelper.Add => BaseCacheManager1.AddInternal => MicrosoftLoggerAdapter.Log
2020-01-13 16:12:40.2954|DEBUG|service:|CacheManager.Redis.RedisCacheBackplane|Backplane is sending 1 messages (0 skipped).||traceid:|requestid:|ExecutionContext.RunInternal => <b__0>d.MoveNext => MicrosoftLoggerAdapter.Log
2020-01-13 16:12:40.2966|DEBUG|service:|CacheManager.Redis.RedisCacheHandle|DB 3 | Failed to add item ['SysRegion:c|包装方式_n|2', exp:Absolute 7.00:00:00, lastAccess:2020-01-13 08:12:40.294] because it exists.||traceid:|requestid:|RetryHelper.Retry => RedisCacheHandle1.Set => MicrosoftLoggerAdapter.Log
I'm using aspnetcore2.1 with cachemanager 1.1.2.
This is my config code:
`Manager = CacheFactory.Build("enjoyDefaultCache", options =>
{
options.WithMicrosoftLogging(loggerFactory)//集成log
.WithUpdateMode(CacheUpdateMode.Up)//指定与上层缓存进行数据同步
.WithMicrosoftMemoryCacheHandle("innerMemoryCache")//一级缓存：内存
.WithExpiration(ExpirationMode.Absolute, TimeSpan.FromHours(2))//2小时过期
.EnableStatistics() //启用统计
//.EnablePerformanceCounters()
.And
.WithRedisConfiguration(CONFIG_KEY_REDIS, config =>
{
var rds = config.WithAllowAdmin()
.WithDatabase(3)
.WithEndpoint(endPoint.Address.ToString(), endPoint.Port);

                           if (!string.IsNullOrWhiteSpace(redisConfigOptions.Password))
                           {
                               rds.WithPassword(redisConfigOptions.Password);
                           }
                       })
                       //.WithMaxRetries(100)
                       //.WithRetryTimeout(50)
                       .WithJsonSerializer()//添加序列化组件，否则初始化rediscachehandle失败
                       .WithRedisBackplane(CONFIG_KEY_REDIS)//使用redis作为基准缓存
                       .WithRedisCacheHandle(CONFIG_KEY_REDIS, true)//二级缓存：声明redis缓存层，并指定为基准缓存
                       .WithExpiration(ExpirationMode.Absolute, TimeSpan.FromDays(7))//一周过期
                       .EnableStatistics() //启用统计
                                           //.EnablePerformanceCounters()
                       ;
            });
        }`

So please give some help,thanks!