Fail to sync an existing directory at ~/Seafile/seafile

[seekstar]

I have a library seafile, and I used to sync it at ~/Seafile/seafile. However, the directory got unsynced recently mysteriously. I tried to sync the library with the existing directory at ~/Seafile/seafile, but the client raise an error:

添加下载任务失败：路径 "/home/searchstar/Seafile/seafile" 与系统路径冲突

which means that the path is in conflict with system paths. Does anyone know why this is happening and how to solve it?

The version of seafile-client is 9.0.3-1.

Update: I also find that after removing ~/Seafile/seafile, trying to sync the seafile library at ~/Seafile/seafile still raises the error:

添加下载任务失败：路径 "/home/searchstar/Seafile" 与系统路径冲突

BTW, I have another account with a library that is also named seafile, and it is synced at ~/seafile/seafile. I don't know whether this is relevant.