EMQX集群版本5.6.0，最近在看broker日志时，发现有这样的日志产生，reason是invalid_ejson，请问这个日志是什么含义，是哪里出了错误呢？
2024-04-28T13:15:40.386503+08:00 [error] clientid:
formal.tips_channel.push_logic.gz100437_monitor, msg: failed_to_execute,
peername: 11.187.132.126:59938, username: push_logic_superuser_ct3xe,
reason: {invalid_ejson,{share,<<"system">>,
<<"$SYS/brokers/+/metrics/messages/qos2/dropped">>}}, stacktrace:
[{jiffy,encode,2,[{file,"jiffy.erl"},{line,100}]},{emqx_utils_json,encode,1,
[{file,"emqx_utils_json.erl"},{line,68}]},{emqx_sys,publish,2,
[{file,"emqx_sys.erl"},{line,351}]},{emqx_hooks,safe_execute,2,
[{file,"emqx_hooks.erl"},{line,205}]},{emqx_hooks,do_run,2,
[{file,"emqx_hooks.erl"},{line,172}]},{emqx_session,subscribe,4,
[{file,"emqx_session.erl"},{line,278}]},{emqx_channel,do_subscribe,3,
[{file,"emqx_channel.erl"},{line,800}]},{emqx_channel,process_subscribe,3,
[{file,"emqx_channel.erl"},{line,786}]},{emqx_channel,handle_in,2,
[{file,"emqx_channel.erl"},{line,517}]},{emqx_connection,with_channel,3,
[{file,"emqx_connection.erl"},{line,846}]},{emqx_connection,process_msg,2,
[{file,"emqx_connection.erl"},{line,495}]},{emqx_connection,process_msg,2,
[{file,"emqx_connection.erl"},{line,501}]},{emqx_connection,handle_recv,3,
[{file,"emqx_connection.erl"},{line,457}]},{proc_lib,wake_up,3,
[{file,"proc_lib.erl"},{line,251}]}], exception: error, failed_call:
{emqx_sys,on_client_subscribed,[#{protocol => mqtt,username =>
<<"push_logic_superuser_ct3xe">>,listener => 'tcp:default',clientid =>
<<"formal.tips_channel.push_logic.gz100437_monitor">>,zone =>
default,peerhost => {11,187,132,126},enable_authn => true,is_superuser =>
false,is_bridge => false,mountpoint => undefined,peerport => 59938,sockport
=> 1883},{share,<<"system">>,
<<"$SYS/brokers/+/metrics/messages/qos2/dropped">>},#{nl => 0,is_new =>
true,qos => 0,rap => 0,rh => 0,sub_props => #{}}]}