ss shows some unix sockets' inode as 0 and rx hang

I have an python app as unix socket server, and several C++ apps as unix socket client. Most of time, it function well. Last week, they ran into an issue. For this issue, what I observed is like:

1. ss shows several the remote socket's inode number as 0 and rxq number is a little high for one of the sockets:

# ss -x | grep -iE "7830816|111729901|112222563"    u_str ESTAB 22928  0                             /var/run/uds_sock 7830816              * 0                   u_str ESTAB 0      0                             /var/run/uds_sock 111729901            * 0                   u_str ESTAB 0      0                             /var/run/uds_sock 112222563            * 0  

2. RX thread in the server is stuck with calling recv(). Actually this is nonblocking socket.

The bt shows like:Thread 401873 (active): "receive_thread"    recv_data (metricsReceiver/internal/client.py:160)        Arguments:            self: <ClientConns at 0x78aa5c1f7460>            conn: <socket at 0x78aa567d6740>            total_len: 753666        Locals:            rcv_len: 255795            res: <bytes at 0x78a8c002bdd0>            READ_LEN: 1000            count: 5            cur: <bytes at 0x78aa607d0030>    recv (/metricsReceiver/internal/client.py:109)        Arguments:            self: <ClientConns at 0x78aa5c1f7460>            conn: <socket at 0x78aa567d6740>        Locals:            msg: <ShaClientV2Msg at 0x78aa5cb71780>            delimiter: <bytes at 0x78aa567c4120>            length: 753666    _wait_for_data (metricsReceiver/internal/connection.py:115)        Arguments:            self: <Connection at 0x78aa5c30e0b0>        Locals:            trace: "Traceback (most recent call last):\n  File "/metricsReceiver/internal/..."            rlist: [96]            elist: []            _: []            sock: 96            conn: <socket at 0x78aa567d6740>            addr: ""    run (threading.py:953)        Arguments:            self: <Thread at 0x78aa5c300a60>    _bootstrap_inner (threading.py:1016)        Arguments:            self: <Thread at 0x78aa5c300a60>    _bootstrap (threading.py:973)        Arguments:            self: <Thread at 0x78aa5c300a60>

The fd causing rx being stuck is one of those sockets' inode as 0：

# lsof -U | grep -iE "7830816|111729901|112222563"python3    401661         sha   96u  unix 0xffff888107badd80      0t0 112222563 /var/run/uds_sock type=STREAM

I do not know what concretely happened cause these, and could not figure out if there is relations between the two phenomenons. Seeking some help here.

DEV os: Ubuntu 22.04.4 LTS

Thanks for your time in advance.