API function trigger.update return "System error"

I use perl-script which use JSON::API to access to Zabbix (BTW calls <item.update> and <graph.update> works fine).

1. call <trigger.get> to get triggers for specified host
2. modify description and comments attribute of one trigger
3. try to update the trigger using <trigger.update>
------------------------------------------------------------
dump of <trigger.update> request and reply
-----------------------------------------------------------
JSON-Request = {
'params' => [
{
'priority' => '4',
'hosts' => [

{ 'hostid' => '10051' }

],
'value' => '2',
'status' => '1',
'templateid' => '0',
'comments' => 'Port speed 80000 bps',
'description' => '[Port FastEthernet0/0.102-802.1Q vLAN subif OutOctets] 009 — TEST QOS int OutOctets Threshold Exceeded',
'lastchange' => '1265182838',
'triggerid' => '18627',
'expression' => '

{19071}>0.75*{19070} & {19070}#0',
'error' => 'Host is unavailable.',
'url' => '',
'type' => '0',
'dep_level' => '0'
}
],
'auth' => 'c5cb68b8d22d2c27402f5a5b1b170360',
'jsonrpc' => '2.0',
'version' => '1.1',
'id' => 7,
'method' => 'trigger.update'
};


JSON-Reply = bless( {
'version' => 0,
'content' => {
'jsonrpc' => '2.0',
'error' => { 'data' => 'JSON-rpc error generation failed. No such error: ', 'message' => 'System error.', 'code' => -32400 },
'id' => 7
},
'jsontext' => '{"jsonrpc":"2.0","error":{"code":-32400,"message":"System error.","data":"JSON-rpc error generation failed. No such error: "},"id":7}',
'is_success' => 0
}, 'JSON::RPC::ReturnObject' );

--------- select from mysql ---------------------------------------

mysql> select * from triggers where triggerid=18627\G
*************************** 1. row ***************************
triggerid: 18627
expression: {19071}

>0.75*

{19070} & {19070}

#0
description: [Port FastEthernet0/0.102-802.1Q vLAN subif OutOctets] 009 OutOctets Threshold Exceeded
url:
status: 1
value: 2
priority: 4
lastchange: 1265182838
dep_level: 0
comments: Port speed 100000000 bps
error: Host is unavailable.
templateid: 0
type: 0
1 row in set (0.00 sec)